A leading Myanmar ethnic rebel army said it had shot down a military helicopter on Monday, a day after a renewed junta crackdown on anti-coup protests left at least five civilians dead.

The Kachin Independence Army (KIA) said it downed the helicopter gunship during fierce clashes near the town of Momauk in the country's far north.

Myanmar has been in turmoil since the military ousted civilian leader Aung San Suu Kyi and seized power on February 1.

Security forces have sought to quell near-daily pro-democracy protests with deadly force, while long-simmering conflicts with ethnic rebels have erupted into fierce fighting.

The KIA, which has waged a decades-long insurgency against the military in northern Kachin state, has been hit by air strikes in recent weeks.

"They used jet fighter and helicopter gunship since eight this morning to attack our troops. Our troops fired back and this was how the helicopter was shot down," said KIA spokesman Col Naw Bu, who refused to give details of the weaponry used to down the chopper.

AFP has tried to contact the Myanmar military to seek their account of events, but has not had a response.

A number of Myanmar's myriad ethnic rebel groups have come out in support of the anti-coup protest movement, offering shelter and even training to activists who have fled the crackdown.

AFP