South Korea’s Joint Chiefs of Staff said the launch occurred from waters near the eastern port city of Sinpo, where North Korea has a major shipyard building submarines.
Defense chiefs from the three countries last week said North Korea’s recent missile tests were destabilizing regional security.
The virtual meeting comes after North Korea earlier this week suggested it might resume nuclear and long-range missile testing that has been paused for more than three years.
The report by North Korean state media came a day after the militaries of the United States, South Korea and Japan said they detected North Korea firing a suspected ballistic missile.
Responding to North Korean missile launches, Fumio Kishida said he had instructed his government to consider all options, including allowing Japanese forces to acquire pre-emptive strike capability.
Wednesday's launches underscored a return of the tensions between the rivals amid a prolonged stalemate in U.S.-led talks aimed at stripping North Korea of its nuclear weapons programme.
Experts say the missiles launched over the weekend resemble in appearance U.S. Tomahawk cruise missiles and are likely designed to overwhelm the missile defences of North Korea's neighbours.
The US Congress reached an agreement to impose new sanctions on Russia for its alleged interference in the 2016 presidential election and its actions in Ukraine.
The US Missile Defense Agency has said that it would soon test an anti-ballistic missile system, days after North Korea demonstrated its arsenal was capable of striking parts of Alaska.
Russian President Vladimir Putin today underlined the importance of staying calm in the North Korea crisis, saying nuclear-armed Pyongyang should be dealt with in a "pragmatic" manner.
The US military has faith that its high-tech defensive systems could fend off any attack from North Korea -- at least for now.
Without giving details of the resolution, Nikki Haley said if the international community is unified, it can cut off the major sources of hard currency to the North Korean regime.
Russia told the UN Security Council today that it opposed new sanctions against North Korea and that a military option was "inadmissible."
The Security Council adopted two sanctions resolutions last year to ramp up pressure on Pyongyang and deny leader Kim Jong-Un the hard currency needed to fund his military programs.
Moon is due to meet with Japanese Prime Minister Shinzo Abe and US President Donald Trump tomorrow evening.