MYANMAR security forces killed a man in the country's main city of Yangon on Monday, media reported, as activists called on ethnic minority forces in the diverse nation to back their campaign against military rule.

After the bloodiest day since last month's military coup with 114 deaths on Saturday, security forces opened fire at a funeral on Sunday, witnesses said.

On Monday, a man was killed and several were wounded when security forces fired in a Yangon neighbourhood, the Democratic Voice of Burma reported.

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

There were small protests on Monday in the central towns of Bago, Minhla and Khin-U, the southern town of Mawlamyine, and Demoso in the east, media portals reported. There were no immediate reports of violence.

Based on a tally by the Assistance Association for Political Prisoners advocacy group, 460 civilians have been killed since the Feb. 1 coup.

The General Strike Committee of Nationalities (GSCN), a main protest group, called in an open letter on Facebook for ethnic minority forces to help those standing up to the "unfair oppression" of the military.

"It is necessary for the ethnic armed organisations to collectively protect the people," the protest group said.

Insurgents from different ethnic minority groups have battled the central government for decades over 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, killing three civilians, after a KNU force overran an army outpost and killed 10 people, an activist group and media said.

Tens of thousands of Karen villagers have lived in camps in Thailand for decades and Prime Minister Prayuth Chan-ocha said he wanted Myanmar's latest problems to remain there.

"Please, let this be an internal problem. We don't want to have an exodus, evacuation into our territory but we will observe human rights, too," Prayuth told reporters in Bangkok.

In Myanmar's north, fighting erupted on Sunday between ethnic Kachin insurgents and the military in the jade-mining area of Hpakant. Fighters from the Kachin Independence Army (KIA) attacked a police station and the military responded with an air attack, Kachinwaves media reported.

There were no reports of casualties.

Both the KNU and KIA have expressed support for the anti-coup movement and called on the army stop the violence against civilian protesters.

'MASS MURDER'

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 last month saying that November elections won by Nobel laureate Aung San Suu Kyi's party were fraudulent, an assertion dismissed by the election commission.

Suu Kyi remains in detention at an undisclosed location and many other figures in her party are also in custody. Their supporters are determined to resist a new phase of military rule that put an end to tentative steps towards democracy over the past decade.

At least six children between the ages 10 and 16 were among those killed in the bloodshed on Saturday, according to news reports and witnesses. Protesters call the victims "Fallen Stars".

On Sunday, mourners fled shooting by security forces at a service for 20-year-old student Thae Maung Maung in Bago near Yangon, people in the town told Reuters. There were no reports of casualties.

U.N. Special Rapporteur for Myanmar Tom Andrews said the army was carrying out "mass murder" and called on the world to isolate the junta and block its access to weapons.

But foreign criticism and sanctions imposed by some Western countries have failed to sway the generals, and neither have the daily protests.

Senior General Min Aung Hlaing, the junta leader, said during a parade to mark Armed Forces Day on Saturday that the military would protect the people and strive for democracy.

Countries including the United States, Britain, Germany and the European Union again condemned the violence.

"It's terrible, it's absolutely outrageous," U.S. President Joe Biden told reporters in Delaware.

The EU's top diplomat, Josep Borrell, called on the generals to stand down from what he called a "senseless path" of violence against their own people.

The top military officer from the United States and nearly a dozen of his counterparts said a professional military "is responsible for protecting - not harming - the people it serves".