More than 500 dead in Myanmar military crackdown against protestors

The death toll in the Myanmar military's crackdown against protesters has passed 500, as armed rebel groups on Tuesday threatened the junta with retaliation if the bloodshed does not stop.

World leaders have ramped up their condemnation of the military's campaign against the anti-coup movement that is demanding the restoration of the elected government and the release of civilian leader Aung San Suu Kyi.

Washington suspended a trade pact with Myanmar and UN chief Antonio Guterres called for a united global front to pressure the junta after more than 100 protesters were killed last weekend.

Adding to that international pressure, a trio of ethnic rebel groups on Tuesday condemned the crackdown and threatened to fight alongside protesters unless the military reined in its violence.

Daily rallies across Myanmar by unarmed demonstrators have been met with tear gas, rubber bullets and live rounds.

The Assistance Association for Political Prisoners said it had confirmed a total of 510 civilian deaths but warned the true toll was probably significantly higher.

Long history of ethnic rebellion

Three of the country's armed ethnic rebel groups -- the Ta'ang National Liberation Army, the Myanmar Nationalities Democratic Alliance Army and the Arakan Army -- issued a joint statement threatening retaliation.

"If they continue to kill the people, we will cooperate with the protesters and fight back," the statement said.

If rebel groups do join the conflict, Debbie Stothard at the International Federation for Human Rights has warned that the situation could degenerate into civil war.

Two dozen ethnic minority rebellions have flared in Myanmar since independence from British colonial rule in 1948.

Calls for a return to democracy

UN Secretary-General Antonio Guterres urged the Myanmar authorities to undertake a "serious democratic transition".

"It is absolutely unacceptable to see violence against people at such high levels, so many people killed," Guterres told a news conference.

"We need more unity... more commitment from the international community to put pressure in order to make sure that the situation is reversed," he said.

US President Joe Biden's administration announced Monday that the 2013 Trade and Investment Framework Agreement, which laid out ways to boost business, would remain suspended until democracy is restored.