Clashes broke out between Myanmar soldiers and an anti-junta civilian militia in the country's second biggest city of Mandalay on Tuesday. According to the military government, four "terrorists" were killed and several personnel from the security forces injured, authorities said.
Security forces raided a house in the city's Chan Mya Tharsi township, following a tip-off, and they were met with small arms fire and grenades, a statement from the junta's information teams said.
"Some security members were seriously injured" in the ensuing battle, it said.
Eight members of the militia, who were in possession of homemade mines, hand grenades and small arms, were also said to be arrested.
The militia, claiming to be Mandalay's new People's Defence Force, said its members responded after the army raided one of its bases.
"We retaliated as one of our guerrilla base camps was invaded," said a post on the group's Facebook page from a person identifying as Major Zeekwat.
Fighting has spread across Myanmar since the February coup, with people forming "defense forces" to combat a brutal military clampdown on dissent. So far, much of the fighting had been confined to small towns and rural areas.
In the last few months, militia groups have launched attacks on soldiers in other places in the country and the army has retaliated with artillery and air strikes, leading to casualties on both sides.
Tens of thousands of people have also been forced to flee from their homes.
The United Nations General Assembly on Friday called for a stop to the flow of arms to Myanmar.
The country's foreign ministry on Saturday released a statement rejecting the UN resolution, saying it was "based on one-sided sweeping allegations and false assumptions."
At least 873 protesters have been killed by security forces since the coup, according to figures from the Assistance Association for Political Prisoners activist group. The junta disputes the tally.