East Timor has declared a state of emergency after police shot and killed at least two student protesters.
The deaths sparked looting and arson across the town of Dili.
Rioters also burned down the house of Prime Minister Mari Alkatiri.
Police had earlier fired on the crowd of around 500 people protesting against the arrest of a student from a school in the city.
"I can confirm that a state of emergency has been imposed," said Vic Josey, the UN acting deputy commissioner of operations.
"We are working in close cooperation with the peacekeeping forces and there is a 7pm curfew imposed."
Earlier, President Xanana Gusmao arrived at the scene of the riots, centred outside the National Police Headquarters, to try to restore order.
The fighting continued, and he was escorted inside the building.
The state of emergency gives security forces extra powers of arrest and the power to impose a curfew.
Mobs also torched the Australian-owned Hello Mister supermarket, which sells mostly expensive imported goods to UN workers and other foreigners in the country. At least one police car was also torched.