YANGON • Rubbish piled up on the streets of Myanmar's main city yesterday after activists launched a "garbage strike" to oppose military rule as the number of pro-democracy protesters killed by the security forces since a Feb 1 coup rose to more than 500.

Security forces shot and killed one man in the southernmost town of Kawthaung as they cleared the streets, the Mizzima news portal reported, and one person was killed in the northern town of Myitkyina, a relative of the 23-year-old victim told Reuters.

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

Myanmar has been in turmoil since the army ousted an elected government led by Nobel laureate Aung San Suu Kyi, reimposing military rule after a decade of tentative steps towards democracy.

At least 512 civilians have been killed in nearly two months of protests against the coup, 141 of them on Saturday, the bloodiest day of the unrest, according to the Assistance Association for Political Prisoners (AAPP) advocacy group.

Alongside the protests, a civil disobedience campaign of strikes has paralysed large parts of the economy. In a new tactic, protesters sought to step up the campaign by asking residents to leave garbage at intersections in the city of Yangon.

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

Pictures on social media showed piles of rubbish building up.

Thousands of protesters came out to march in several other towns yesterday, according to media and photos online.

On Monday, 14 civilians were killed, including at least eight in Yangon's South Dagon neighbourhood, the AAPP said.

Security forces there fired a heavier calibre weapon than usual towards protesters crouching behind a barricade of sand bags, witnesses said. It was not immediately clear what weapon was used but it was believed to be some type of grenade launcher.

State media 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 said yesterday there had been no pause in the crackdown.

"There was shooting all night," said the resident, who declined to be identified.

Residents found a badly burned body in the morning, the witness said, adding it was not known what had happened to the person and the military took the body away.

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

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 military's "unfair oppression".

In a sign that the call may be gaining traction, three groups - the Myanmar National Democratic Alliance Army, the Arakan Army and the Ta'ang National Liberation Army - in a joint statement urged the military to stop killing protesters and resolve political issues.

If not, they said, they would cooperate with all ethnic groups "who are joining Myanmar's spring revolution" to defend themselves.

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

Myanmar military aircraft bombed a KNU area on the weekend and thousands of villagers have sought refuge in caves, an activist group said, while some 3,000 fled to neighbouring Thailand.

A Myanmar toddler miraculously survived a weekend air strike that killed his father in their bamboo hut in Karen State.

The boy, Saw Ta Eh Ka Lu Moo Taw, almost three years old, lives in the Day Bu Doh valley with his farmer parents.

"He was sitting on his dad's lap at the time and the shrapnel from the bomb killed his father. (The boy) has lacerations to his neck and has some fragments still in him," Mr David Eubank from the Free Burma Rangers told Agence France-Presse, saying the father, Mr Saw Aye Lay Htoo, 27, died instantly.

The humanitarian group is providing medical treatment to the boy.

Myanmar's military has for decades justified its grip on power by saying it is the only institution capable of preserving national unity.

REUTERS, AGENCE FRANCE-PRESSE