Fighters opposed to Myanmar's military junta seized a police station in the town of Mobye on Sunday, killing at least 13 security force soldiers, according to local media.
The insurgents also claimed they had managed to capture four soldiers as part of their operation.
The onslaught is part of a wider upsurge in violence that has taken place since the February 1 coup that overthrew elected leader Aung San Suu Kyi.
Also on Sunday, a gun battle broke out near the Chinese border. And on Saturday an armed ethnic group opposed to the junta launched an attack on a jade mining town near Myanmar's Indian border.
Footage shows how violent events unfolded
Video from Mobye showed the uniformed corpses of the security forces, while other images showed four men, who were said to be police officers, with their hands behind their backs and blindfolded.
In another picture from Mobye, a police vehicle was shown ablaze.
Media outlet Irrawaddy quoted a soldier from the local People's Defense Force as saying the police station had been set alight and that two civilians had been injured in the struggles.
Mobye lies some 100 kilometers (60 miles) east of Naypyidaw, Myanmar's capital. It is situated near territory held by some of the ethnic armed groups that have battled for greater autonomy over several decades.
An alliance of four ethnic groups opposing the military, fought early on Sunday with security forces in Muse, one of the main border crossings into China, local media reported.
Since the army seized power almost four months ago, local People's Defense Forces, acting as rebel groups, have sprung up to oppose the junta, often armed with shotguns and homemade weapons.
Myanmar has witnessed daily protests since the military coup while nationwide strikes have hamstrung hospitals, schools and private businesses.
Reuters contributed to this report.