The UN envoy on Myanmar implored the Security Council to take action Wednesday in the Asian nation's escalating crisis, warning of the risk of civil war and an imminent "bloodbath" as the junta violently represses pro-democracy protests.
More than 520 people have died in daily demonstrations since the military overthrew elected leader Aung San Suu Kyi on February 1, halting Myanmar's decade-old experiment in democracy.
"I appeal to this Council to consider all available tools to take collective action and do what is right, what the people of Myanmar deserve and prevent a multi-dimensional catastrophe," special envoy Christine Schraner Burgener told the closed-door session, according to remarks obtained by AFP.
She said she remained open for dialogue with the junta but added: "If we wait only for when they are ready to talk, the ground situation will only worsen. A bloodbath is imminent."
Earlier Wednesday, Suu Kyi's legal team said the ousted leader appeared to be in good health despite two months of detention.
Suu Kyi, 75, has not been seen in public since she was deposed but a member of her legal team, Min Min Soe, was summoned to a police station in the capital Naypyidaw for a video meeting with her.
"The physical situation of DASSK (Suu Kyi) seemed good according to her appearance on video screen," her legal team said in a statement.
Suu Kyi is facing a raft of criminal charges, and conviction could see her barred from political office for life.
The coup and the junta's subsequent actions have triggered international condemnation.
Britain called for Wednesday's emergency Security Council session after the military dramatically ramped up its use of lethal force against protesters over the weekend.
In another violent escalation, Myanmar's military Saturday launched the first air strikes in Karen state in 20 years after a rebel group seized a military base -- raising fears of a return to armed ethnic conflict in the ethnically diverse nation.
"The military's cruelty is too severe and many (armed ethnic fighters) are taking clear stances of opposition, increasing the possibility of civil war at an unprecedented scale," Burgener said.
"Failure to prevent further escalation of atrocities will cost the world so much more in the longer term than investing now in prevention, especially by Myanmar's neighbors and the wider region."
Meanwhile, a group of ousted MPs from Suu Kyi's National League for Democracy (NLD), who have been working underground against the junta, said they would form "a new civilian government" in the first week of April, without giving further details.
The Committee for Representing Pyidaungsu Hluttaw (CRPH), the Burmese word for "parliament", also warned that "serious action" would be taken against those who are not part of the protest movement.
World powers have repeatedly condemned the violent crackdown on dissent and hit junta figures with sanctions, but so far the pressure has not swayed the generals.
The US State Department has ordered the departure of non-essential diplomatic staff and their families from Myanmar, and Japan -- a top donor to the country -- has halted new aid payments.
As well as imposing targeted sanctions, the US also has suspended a trade pact with Myanmar.
Linda Thomas Greenfield, the US ambassador to the United Nations, raised the possibility of action if the military does not step down.
"We're hopeful that the situation will eventually resolve and the military will go back to their barracks and allow the democratically elected government to take its place," she told reporters.
"But if they do not do that, and they continue the attacks that they were making on civilian populations, then we have to look at how we might do more," she said.
The mounting bloodshed has also angered some of Myanmar's 20 or so armed ethnic groups, who control large areas of territory mostly in border regions.
Three of them -- the Ta'ang National Liberation Army (TNLA), the Myanmar Nationalities Democratic Alliance Army and the Arakan Army -- on Wednesday looked set to join the protesters' fight.
Brigadier General Tar Bhone Kyaw from the TNLA told AFP that all three would end their ceasefire with the military.
"If they continue to kill the people, we have no reason to extend unilateral ceasefire with them," he said.
Two other outfits -- the Karen National Union (KNU) and the Kachin Independence Army (KIA) -- have already stepped up attacks on military and police in recent days.
Following the weekend air strikes, about 3,000 people fled through the jungle to seek safety across the border in Thailand.
Thai authorities say around 2,400 have returned "voluntarily" to Myanmar, and another 200 have also agreed to go back.
Thai police said they had intercepted 10 parcels containing 112 grenades and 6,000 rounds of ammunition in northern Chiang Rai province that had been destined for Myanmar's notorious border town Tachileik.