YANGON: Hundreds of peaceful anti-coup protesters were cordoned by Myanmar security forces in Yangon on Monday, the UN said, warning they were "deeply concerned" about their fate.
The country has been in turmoil since a February 1 coup ousted civilian leader Aung San Suu Kyi and triggered mass protests against the new military junta.
The police and military have responded with an increasingly brutal crackdown on demonstrators, with more than 50 people killed and nearly 1,800 arrested.
As demonstrators across the country sought to paralyse the economy with strike action following a weekend of night raids and arrests, security forces blocked around 200 protesters in San Chaung township in the commercial hub of Yangon from leaving.
Sharp loud bangs could be heard coming from the area, according to an AFP reporter, although it's unclear if the sounds were caused by gunfire or stun grenades.
Repeated screaming was audible in a live Facebook stream.
"I just escaped from Sanchaung," wrote Maung Saungkha, an activist, on Twitter.
"Almost 200 young protesters are still blocked by the police and soldiers there. Local and international community needs to help them now!"
The UN and embassies in Yangon -- including the US and former colonial power Britain -- urged security forces to free the demonstrators, many of whom had taken shelter in the homes of local residents.
"We are deeply concerned about the fate of some 200 peaceful protesters -- incl. women -- who have been cordoned by security forces in Yangon, and may be at risk of arrest or ill-treatment," the UN rights office said in a tweet.
"We urge the police to immediately allow them to leave safely and without reprisals."
The statement came after three protesters were shot dead on Monday.
In the northern city of Myitkyina, security forces used tear gas and opened fire during street clashes with stone-throwing protesters.
There was grisly footage of bleeding bodies lying on beds as health workers frantically tried to resuscitate them.
One man was also seen lying face down, with part of his skull blown out.
A poignant image in local media showed a Catholic nun in a white habit on her knees in the street, pleading with police to show restraint.
"Two men were shot dead on the spot, meanwhile three others including a woman were shot in the arm," a medic told AFP.
A third protester was shot dead in the town of Pyapon in the Irrawaddy Delta region, an eyewitness and a rescue official told AFP.
- General strike call -
It was also a dark day for independent media in the country, as security forces raided the office of Myanmar Now in Yangon.
The outlet later had its publishing licence revoked, as did independent media Mizzima, DVB, Khit Thit and 7 Day, following an information ministry order, state broadcaster MRTV said.
That followed the closure of banks, stores, shopping malls and some clothing factories Monday after an appeal by trade unions for a general strike to bring the economy to a standstill.
"To continue economic and business activities as usual... will only benefit the military as they repress the energy of the Myanmar people," 18 unions said in a statement.
"The time to take action in defence of our democracy is now."
Unions are seeking to ramp up an ongoing "Civil Disobedience Movement" -- a campaign urging civil servants to boycott working under military rule -- which has already hit state machinery hard.
The impact has been felt at every level of the national infrastructure, with hospital disruptions, empty ministry offices, and banks unable to operate.
The junta has warned that civil servants "will be fired" with immediate effect Monday if they continue to strike.
Physicians for Human Rights said it was appalled by security forces occupying public hospitals, calling the move a violation of international law.
"Even though medical personnel vacated their government posts to initiate the civil disobedience movement, many returned to government hospitals in response to escalating violence against peaceful protestors," the group said,
State-run media confirmed the hospital takeovers.
- International pleas -
The coup and subsequent crackdown have drawn widespread international condemnation as well as sanctions against key military personnel.
Australia's Foreign Minister Marise Payne announced late Sunday the country was suspending its defence cooperation programme with Myanmar, which included English language training.
Canberra is reviewing its aid programme so money is channelled away from government agencies towards not-for-profit organisations.
The military, which denies responsibility for loss of life in the protests, has defended seizing power by alleging widespread electoral fraud in November's elections, which Suu Kyi's party had won in a landslide.
The Nobel laureate has not been publicly seen since she was detained as the lightning coup was launched in the early hours of February 1.