WASHINGTON: The Ukrainian government is closing airports in eastern Ukraine from midnight through 7 a.m. because of the confrontation with Russia.
Ukrainian aviation authorities also have declared some airspace in the east to be "danger areas" because of attempts by Russian aviation authorities to seize control of the airspace.
Ukraine acted after Russia issued a ban on civilian air traffic in airspace over eastern Ukraine.
The announcement Wednesday night establishes buffer zones for traffic controlled by Ukrainian authorities to avoid coming into potentially hazardous conflict with air traffic controlled by Russian authorities.
Last week, Ukrainian aviation officials warned pilots in the region to be on the lookout for Russian authorities trying to take control of the airspace and to only recognise Ukraine's controllers.
With the Russian threat growing, the Ukrainian president is pleading for peace and says Russian President Vladimir Putin would not accept his call.
In an emotional address to the nation late Wednesday, Ukrainian President Volodymyr Zelenskyy rejected Moscow's claims that his country poses a threat to Russia and lamented that a Russian invasion would cost tens of thousands of lives.
"The people of Ukraine and the government of Ukraine want peace," he said in Russian, hours after declaring a nationwide state of emergency.
But if the nation comes under an attack, "we will fight back. Zelenskyy said he tried to call Putin, but the Kremlin remained silent."
The Kremlin said rebels in eastern Ukraine asked Russia for military assistance Wednesday to help fend off Ukrainian "aggression," an announcement that immediately fuelled fears that Moscow was offering up a pretext for war, just as the West had warned.
A short time later, the Ukrainian president rejected Moscow's claims that his country poses a threat to Russia and said a Russian invasion would cost tens of thousands of lives.
"The people of Ukraine and the government of Ukraine want peace," President Volodymyr Zelenskyy said in an emotional overnight address to his nation in Russian.
"But if we come under attack, if we face an attempt to take away our country, our freedom, our lives and lives of our children, we will defend ourselves. When you attack us, you will see our faces, not our backs."
Zelenskyy said he asked to arrange a call with Russian President Vladimir Putin late Wednesday, but the Kremlin did not respond.
In an apparent reference to Putin's move to sanction the deployment of the Russian military to "maintain peace" in eastern Ukraine, Zelensky warned that "this step could mark the start of a big war on the European continent."
"Any provocation, any spark could trigger a blaze that will destroy everything," he said.
He challenged the Russian propaganda claims, saying that "you are told that this blaze will bring freedom to the people of Ukraine, but the Ukrainian people are free."
The United Nations Security Council quickly scheduled an emergency meeting Wednesday night at Ukraine's request.
Ukrainian Foreign Minister Dmytro Kuleba called the separatists' request "a further escalation of the security situation."
Anxiety about an imminent Russian offensive against its neighbor soared after Putin recognised the separatist regions' independence on Monday, sanctioned the deployment of troops to the rebel territories and received parliamentary approval to use military force outside the country.
The West responded with sanctions.
Kremlin spokesman Dmitry Peskov said the rebel chiefs wrote to Putin on Wednesday, pleading with him to intervene after Ukrainian shelling caused civilian deaths and crippled vital infrastructure.
White House press secretary Jen Psaki said the separatists' request for Russian help was an example of the sort of "false-flag" operation that the U.S. and its allies have expected Moscow to use as a pretense for war.
"So we'll continue to call out what we see as false-flag operations or efforts to spread misinformation about what the actual status is on the ground," she said.
Earlier in the day, Ukrainian lawmakers approved a decree that imposes a nationwide state of emergency for 30 days starting Thursday.
The measure allows authorities to declare curfews and restrictions on movement, block rallies and ban political parties and organisations "in the interests of national security and public order."
The action reflected increasing concern among Ukrainian authorities after weeks of trying to project calm.
The Foreign Ministry advised against travel to Russia and recommended that any Ukrainians who are there leave immediately.
"For a long time, we refrained from declaring a state of emergency, but today the situation has become more complicated," Ukrainian National Security and Defense Council head Oleksiy Danilov told parliament, emphasising that Moscow's efforts to destabilise Ukraine represented the main threat.
Pentagon press secretary John Kirby said the Russian force of more than 150,000 troops arrayed along Ukraine's borders is in an advanced state of readiness.
"They are ready to go right now," Kirby said.
The latest images released by the Maxar satellite image company show Russian troops and military equipment deployed within 10 miles of the Ukrainian border and less than 50 miles from Ukraine's second-largest city, Kharkiv.
In other developments, Russia evacuated its embassy in Kyiv; Ukraine recalled its ambassador to Russia and considered breaking all diplomatic ties with Moscow and dozens of nations further squeezed Russian oligarchs and banks out of international markets.
President Joe Biden allowed sanctions to move forward against the company that built the Russia-to-Germany Nord Stream 2 gas pipeline and against the company's CEO.
"As I have made clear, we will not hesitate to take further steps if Russia continues to escalate," Biden said in a statement.
Germany said Tuesday it was indefinitely suspending the project, after Biden charged that Putin had launched "the beginning of a Russian invasion of Ukraine" by sending troops into the separatist regions.
The pipeline is complete but has not yet begun operating.
Putin said Tuesday he had not yet sent any Russian troops into the rebel regions, contrary to Western claims, and Donetsk rebel leader Denis Pushilin insisted Wednesday there were no Russian troops in the region even though a local council member claimed the previous day they had moved in.
Ukrainian Minister for Digital Transformation Mykhailo Fedorov said a wave of denial-of-service attacks targeted official websites and some banks Wednesday.
The attack knocked offline the sites of the parliament, cabinet and Foreign Ministry and caused interruptions or delays to the sites of the defense and interior ministry, which controls the police.
Already, the threat of war has shredded Ukraine's economy and raised the specter of massive casualties, energy shortages across Europe and global economic chaos.
European Union sanctions against Russia took effect, targeting several companies along with 351 Russian lawmakers, who voted for a motion urging Putin to recognise the rebel regions, and 27 senior government officials, business executives and top military officers.
The Russian Foreign Ministry has shrugged off the sanctions, saying that "Russia has proven that, with all the costs of the sanctions, it is able to minimise the damage."
In Ukraine's east, one Ukrainian soldier was killed and six more were injured after rebel shelling, the Ukrainian military said.
Separatist officials reported several explosions on their territory overnight and three civilian deaths.
Facing a barrage of criticism at the 193-member United Nations General Assembly, Russia's U.N. ambassador Vassily Nebenzia warned Ukraine that Russia will monitor a cease-fire in the east and emphasised that "no one intends to go softly, softly with any violators."
"A new military adventure" by Kyiv "might cost the whole of Ukraine very dearly," he warned ominously.
After weeks of rising tensions, Putin's steps this week that dramatically raised the stakes.
He recognised the independence of those separatist regions, a move he said extends even to the large parts of the territories now held by Ukrainian forces, and had parliament grant him authority to use military force outside the country.
Putin laid out three conditions that he said could end the standoff, urging Kyiv to recognise Russia's sovereignty over Crimea, the Black Sea peninsula that Moscow annexed from Ukraine in 2014, to renounce its bid to join NATO and to partially demilitarise.
Ukraine long has rejected such demands.
The UN Security Council scheduled an emergency meeting on Ukraine for Wednesday night, just hours after diplomats from dozens of countries took the floor at the General Assembly to deplore Russia's actions toward the country and plead for diplomacy as fears of a new war in Europe grew.
Citing an "immediate threat of Russian offensive," Ukraine requested the council session after Russia said that rebels in eastern Ukraine had asked Moscow for military assistance.
The council, where Russia holds the rotating presidency this month, was meeting just two days after another emergency session saw no support for Russia's decision to recognise two rebel regions of Ukraine as independent and to order Russian troops there for "peacekeeping."
Council diplomats are now finalising a draft of a resolution that would declare that Russia is violating the UN Charter, international law, and a 2015 council resolution on Ukraine, a diplomat said, speaking on condition of anonymity because the discussions were private.
The resolution would urge Russia to come back into compliance immediately, the diplomat said.
At the General Assembly meeting earlier Wednesday, Russia and ally Syria defended Moscow's moves.
But even China, which usually takes Russia's side at the U.N., spoke up for the world body's longstanding principle of respecting countries' sovereignty and internationally recognised borders, while not mentioning Russia by name.
Meeting a day after Western powers and some other countries imposed new sanctions on Russia, the 193-member General Assembly didn't take any collective action.
But the comments from nearly 70 nations, with more scheduled for Monday, represented the broadest forum of global sentiment since the crisis dramatically escalated this week.
Countries from Guatemala to Turkey to Japan condemned Russia's embrace of the separatist regions' independence claims or voiced support for Ukraine.
"Ukraine, you're not alone," Bulgarian Ambassador Lachezara Stoeva said.
U.S. Ambassador Linda Thomas-Greenfield exhorted countries "to get off the sidelines."
"There is no middle ground here. Calling for both sides to de-escalate only gives Russia a pass. Russia is the aggressor here," she said.
Thomas-Greenfield warned that the confrontation could spiral into a refugee crisis, estimating that as 5 million people could be displaced and could make food prices spike in developing countries where Ukraine supplies wheat.
Echoing a narrative being broadcast to Russians at home, Russian Ambassador Vassily Nebenzia portrayed his country as responding to the plight of beleaguered people in the breakaway areas.
Russia claims Ukraine is engaging in violence and oppression, which Ukraine denies.
"We urge you today to focus on reining in Kyiv," Nebenzia said.
Syria accused the West of using the assembly to pressure Moscow.
"The Ukrainian crisis was created by the Western states, led by the United States, to divide people and to undermine Russian security," Ambassador Bassam al-Sabbagh said.
Ukrainian Foreign Minister Dmytro Kuleba implored countries to use tough economic sanctions, strong messages and "active diplomacy" to get Russia to back off.
A lackluster response would jeopardise not only Ukraine but the concept of international law and global security, he warned.
"We need to use this last chance for action and stop Russia where it is," Kuleba said.
Russia seized Ukraine's Crimea Peninsula in 2014, and pro-Russia rebels have since been fighting Ukrainian forces in the eastern areas of Donetsk and Luhansk.
More than 14,000 people have been killed in the conflict.
After weeks of rising tension as Moscow massed over 150,000 troops on Ukraine's borders, Russian President Vladimir Putin on Monday recognised the two regions' independence and ordered Russian forces there as what he called "peacekeepers."
U.N. Secretary-General Antonio Guterres disputed that, saying they are troops entering another country without its consent.
"Our world is facing a moment of peril," Guterres told the assembly.