Myanmar junta troops have clashed with fighters from a major militant group in Rakhine state, breaking a ceasefire that kept the peace in the western region since the coup, a rebel spokesman said on Wednesday.

The Southeast Asian country has been in chaos since the February putsch, with a brutal crackdown on dissent and increased fighting in borderlands involving ethnic armed organisations.

Days after the coup, the junta reaffirmed a commitment to a ceasefire with the Arakan Army (AA), which has fought a bloody war for autonomy for Rakhine state's ethnic Rakhine population.

The ceasefire freed up military troops to battle local "self-defence forces" that have sprung up across the country in opposition to the military.

"Around 11:00am yesterday, there was a clash for a few minutes in the north of Maungdaw," an AA spokesman told AFP.

"It was because the Myanmar military entered the area. Casualty details are not known yet."

Clashes between the AA and the military in 2019 displaced over 200,000 people across the state, one of Myanmar's poorest.

"I think it's getting a little testy, but so far may not escalate if the Tatmadaw don't have the troops / firepower to really take on the AA," said analyst David Mathieson, using another name for Myanmar's military.

The junta ended a 19-month internet shutdown in the state of around one million after the coup.

The regime has also announced that a member of a local Rakhine nationalist party will be joining its cabinet.

Rakhine state, home to both the Rohingya and a largely Buddhist ethnic Rakhine majority, has been a tinderbox of conflict for decades.

The military drove out more than 740,000 Rohingya Muslims from the state in a 2017 campaign that United Nations investigators have called genocide.

Rights groups have also accused soldiers of committing war crimes including extrajudicial killings in their later campaign against the AA.