Six opposition rebels have been killed after days of clashes in Myanmar, an anti-junta defence force made up of civilians said Sunday, as Britain and the United States condemned the military's violence against civilians.

The country has been in an uproar since the military ousted civilian leader Aung San Suu Kyi in a February 1 coup, triggering a massive uprising that authorities have sought to quell with lethal force. 

Some in the anti-junta movement have set up local militias armed with homemade weapons to protect their towns from security forces -- which have killed at least 790 civilians according to a local monitoring group.

In the western state of Chin, the town of Mindat has emerged as a hotspot for unrest, where some residents have formed the Chinland Defence Force (CDF).

"Six members of our CDF who tried to protect the security of the people in Mindat attacked (junta forces) and sacrificed their lives for the national revolution," said a CDF statement on Sunday. 

A spokesman also told AFP that over 10 have been wounded this week, while five Mindat residents were arrested by the military.

With mobile data blocked across the country, details about the fighting have been slow to come out, and on-the-ground verification is made harder as locals are fearful of retaliation.

The spokesman, who declined to be named, said CDF fighters set fire to several army trucks, destroying them, and ambushed reinforcement troops, while the military has attacked the town with artillery.

By Sunday, the CDF had retreated into the jungle, he said.

"We will not stay any more in the town... but we will come back to attack soon," he said. "We only have homemade guns. This was not enough." 

He added that residents remaining in Mindat -- which has been under martial law since Thursday -- were afraid to leave their homes for fear of being targeted by the military. 

- Violence 'cannot be justified' -
The US and UK embassies in Myanmar sounded the alarm Saturday on Mindat's unrest, calling for security forces to cease violence.

"The military's use of weapons of war against civilians, including this week in Mindat, is a further demonstration of the depths the regime will sink to to hold onto power," the US embassy said in a tweet Saturday.

"Attacks on civilians are illegal and cannot be justified," said the British embassy, referring to reports of violence from Mindat.

"Evidence of atrocities should be sent to the (United Nations Independent Investigative Mechanism for Myanmar) so perpetrators can be held to account," the embassy tweeted, referring to a committee that collects evidence of international crimes.

State-run newspaper New Light of Myanmar reported Sunday that a military tribunal would be convened to try "perpetrators of terrorist attacks" in Mindat.

Security forces saw multiple attacks which left one man dead, said the newspaper, and an ambush on Friday by "1,000 rioters" killed some soldiers -- though it did not say how many. 

Across the country, anti-coup protesters continue to march for democracy -- with demonstrators in northern Hpakant holding signs that said "Stay strong, Mindat".

Pope urges peace, unity

Pope Francis celebrated mass in honour of conflict-ridden Myanmar Sunday, repeating his calls for peace and an end to the violence that has left hundreds dead in nearly four months.

The mass inside Saint Peter's Basilica at the Vatican came after several appeals for peace in recent months by Francis, who visited Myanmar in November 2017, marking the first papal visit to a Buddhist-majority nation.

A Myanmar nun recited the first reading in Burmese in front of a congregation of about 200 nuns, priests and seminarians during the mass intended for the country's Catholics in Rome and beyond.

Myanmar has been in chaos since the military ousted civilian leader Aung San Suu Kyi in a February 1 coup, triggering a massive civilian uprising that security forces have sought to quell with lethal force.

Street protests calling for a return to democracy continue to occur nearly daily, despite the junta’s bloody crackdown having killed an estimated 790 people to date, according to a local monitoring group.

In his homily, Francis skirted an overt denunciation of the military regime, instead appealing to the faithful to be "steadfast in the truth," urging them not to lose hope.

"Dear brothers and sisters, in these days when your beloved country of Myanmar is experiencing violence, conflict and repression, let us ask ourselves: what we are being called to keep? In the first place, to keep the faith," he said. 

Francis appealed for unity, calling division among communities and peoples "a deadly disease."

"Sins against unity abound: envy, jealousy, the pursuit of personal interests rather than the common good, the tendency to judge others. Those little conflicts of ours find a reflection in great conflicts, like the one your country is experiencing in these days," he said.

"I know that some political and social situations are bigger than we are," he added. "Yet commitment to peace and fraternity always comes from below: each person, in little things, can play his or her part."

"Amid war, violence and hatred, fidelity to the Gospel and being peacemakers calls for commitment, also through social and political choices, even at the risk of our lives."