A provincial office of East Timor's ruling Fretilin party has been torched south of the capital, a lawmaker said.
The UN says more troops are needed to control the unrest
Youths looted and burned the office in Gleno, Ermera district, Parliament's Speaker Francisco Guterres said.
It was the first reported violence outside the capital, Dili, since a wave of unrest erupted last month.
The UN has said more peacekeepers will be needed to end the unrest, which has left over 20 people dead.
More than 2,000 foreign troops, mostly from Australia, are already in Dili.
The crisis was triggered by the sacking of 600 striking soldiers in March. It spread to different factions of the security forces and led to gang violence in Dili.
Mr Guterres said the house of a party official in Ermera, which is about 40km (25 miles) south west of Dili, was also attacked and that there had been gunfire in the streets.
Feb: More than 400 troops strike over pay and conditions
March: Government sacks nearly 600 of 1,400-man army
April: Rioting by sacked troops leaves five people dead
May: Violence intensifies, with battles between gangs from east and west of the country
24 May: Government asks foreign troops to take control
"I condemn those who attacked my representative in Ermera district and burned down our office," he said.
Rebel troops based in Gleno denied any involvement in the violence, with one of them questioning whether the incident was merely propaganda.
The government has been blamed for the violence and many protesters are calling for the resignation of Prime Minister Mari Alkatiri.
But a spokesman for Mr Alkatiri told AFP that the prime minister was not intending to meet a deadline set by the protesters for his resignation.
On Wednesday, a United Nations official said that Secretary-General Kofi Annan felt more UN peacekeepers were needed to control the unrest in East Timor.
"The council will have to make some decision as to what the UN posture in East Timor will look like in the months ahead, but it is pretty clear already from here that that will have to be increased," spokesman Stephane Dujarric told reporters.
The violence is the worst since East Timor's bloody separation from Indonesia in 1999.