Security forces in Myanmar, backed by armored vehicles, have clashed with a local militia in the city of Mandalay.
The military government said soldiers were met with small arms fire and grenades when they raided a house.
It said troops killed four people and arrested eight others.
The BBC's Nick Marsh reports.
The People's Defense Forces were set up last month to form the armed wing of a new underground parallel government in Myanmar.
Until today, their opposition to the country's military leadership had been limited to fighting in rural areas or small towns.
But this time, it was urban clashes in the middle of Myanmar's second biggest city.
According to local reports, military junta troops surrounded a boarding school being used as a base by the militia.
The response was an exchange of gunfire and unconfirmed reports of casualties.
It marks a new stage of resistance to this year's coup.