The Office of Commander-in-Chief issued a statement yesterday that KIA/TNLA insurgent groups jointly carried out attacks on a police camp on Pankham Bridge, head of Nankham Myoma People's Militia Group U Aike San's house, Manwain gate and Naungyan village near Pankham Bridge.
Rights defenders said clashes in the north have ramped up since January, as the worldwide community focusses on the Rohingya crisis in the west of the country.
The military stands accused of carrying out an ethnic cleansing campaign against the stateless minority in Rakhine.
Pictures of burned out vehicles and armed men running for cover spread quickly on social media. The sound of automatic gunfire filled the air as ambulances picked up the wounded.
Fifteen civilians, including two women, were killed, and 20 were injured, he said, citing information from police.
He called the operation "terrorism". "They ran away after attacking the civilian targets", said Zaw Htay.
The TNLA claimed that its attack was a response to the Myanmar Army's recent offensives against the Kachin Independence Army, which is one Myanmar's most powerful ethnic minority armed groups. "It is just a destructive terrorist attack".
Aye Myint, a police officer in Muse, said the death toll was 19, and that TNLA fighters used small arms as well as mortars.
TNLA spokesman Major Mai Aik Kyaw told AFP that the group attacked joint military and militia posts in the Shan state town of Muse and on a road to Lashio. The fighting has displaced thousands of people in the past month. "We are sorry. But it's hard to say how they were killed during the fighting", said the TNLAA spokesman.
Myanmar's patchwork of ethnic groups make up around a third of the population.