Myanmar death toll tops 500 as protesters stage 'garbage strike'

Out of 14 civilians killed in Myanmar on Monday, the Assistance Association for Political Prisoners (AAPP) said at least eight were in the South Dagon district of Yangon.

Security forces in the area fired a much heavier-calibre weapon than usual on Monday to clear a barricade of sand bags, witnesses said. It was not immediately clear what type of weapon was used.

State television said security forces used "riot weapons" to disperse a crowd of "violent terrorist people" who were destroying a pavement and one man was wounded.

A South Dagon resident on Tuesday said more gunfire could be heard in the area overnight raising concerns of more casualties.

Police and a junta spokesman did not answer calls seeking comment.

U.N. Secretary-General Antonio Guterres urged Myanmar's generals to stop the killings and repression of demonstrations.

In a new tactic, protesters sought to step up a civil disobedience campaign on Tuesday by asking residents to throw garbage onto streets on key road intersections.

"This garbage strike is a strike to oppose the junta," read a poster on social media.

The move comes in defiance of calls issued via loudspeakers in some neighbourhoods of Yangon on Monday urging residents to dispose of garbage properly.

At least 510 civilians had been killed in nearly two months of efforts to stop protests, advocacy group AAPP said.

The total killed on Saturday, the bloodiest day so far, had risen to 141, its figures showed.

One of the main groups behind the protests, the General Strike Committee of Nationalities, called on Monday in an open letter for ethnic minority forces to help those standing up to the "unfair oppression" of the military.

In a sign that the call may be gaining more traction, three groups in a joint letter on Tuesday called on the military to stop killing peaceful protesters and resolve political issues.

The groups - which include the Myanmar National Democratic Alliance Army, the Arakan Army and Ta’ang National Liberation Army - warned if the military did not do this they "will cooperate with all nationalities who are joining Myanmar's spring revolution in terms of self defence."

Insurgents from different ethnic groups have battled the central government for decades for greater autonomy. Though many groups have agreed to ceasefires, fighting has flared in recent days between the army and forces in both the east and north.

Heavy clashes erupted on the weekend near the Thai border between the army and fighters from Myanmar's oldest ethnic minority force, the Karen National Union (KNU).

About 3,000 villagers fled to Thailand when military jets bombed a KNU area after a KNU force overran an army outpost and killed 10 soldiers, an activist group and media said.

Thai authorities denied accounts by activist groups that more than 2,000 refugees had been forced back, but a Thai official said it was government policy for the army to block them at the border and deny access to outside aid groups.

Myanmar's military has for decades justified its grip on power by saying it is the only institution capable of preserving national unity. It seized power saying that November elections won by Nobel laureate Aung San Suu Kyi's party were fraudulent, an assertion dismissed by the election commission.

U.S. Trade Representative Katherine Tai said the United States was suspending all trade engagement with Myanmar until the return of a democratically elected government.