Kachin Independence Army, the armed wing of the Kachin Independence Organisation, attacked a police station in Shwegu township and seized weapons and supplies, and wounded one police officer
Since the takeover six weeks ago, Myanmar has been under a nationwide state of emergency, with its civilian leaders ousted and detained and military leaders in charge of all government.
Myanmar has been roiled by protests, strikes and other acts of civil disobedience since the coup toppled Suu Kyi's government on February 1 just as it was to start its second term.
Bagan is best known for being one of the country's top tourist attractions, but it has also been the scene of large protest marches against the military's February 1 seizure of power.
State railway workers on Sunday had called a strike, joining a loosely organised Civil Disobedience Movement that was initiated by medical workers and is the backbone of the resistance.
Suu Kyi, who was ousted in a military coup on February 1, has already been charged with possessing walkie-talkies that were imported without being registered.