Clashes in Northern Myanmar near the border with China have increased since January, as the worldwide community pays more attention to the Rohingya refugee crisis in the West.
Fifteen civilians, including two women, were killed, and 20 were injured, he said, citing information from police.
The Ta'ang National Liberation Army is one of several in Myanmar's frontier areas that have long battled government forces.
Human rights groups on Saturday urged Myanmar to drop charges against activists protesting military offensives in Kachin State, which borders Shan State.
Pictures of burned out vehicles and armed men running for cover spread quickly on social media.
He called the operation "terrorism". In the past few months, clashes between rebels and the military in Myanmar's northeastern region have intensified, resulting in thousands of displaced in neighbouring Kachin state. "They ran away after attacking the civilian targets", said Zaw Htay.
"Fighting took place since 5am this morning at three places: two military bases in Muse and one near a bridge on the way to Lashio town", TNLA spokesman Major Mai Aik Kyaw told AFP. "It is just a destructive terrorist attack".
Those fleeing violence have sheltered in tents and even churches in Kachin, which is mainly Christian, as rights groups accuse the military of blocking aid.
The security police fought back against insurgents in cooperation with Paysay People's Militia Group and Myoma People's Militia Group. "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 round a third of the population, but the Bamar or Burmese have filled the Buddhist-majority country's power structures since independence in 1948.
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