By Tito Belo

DILI, July 23 (Reuters) - Security forces in East Timor fired tear gas and rubber bullets after 13 people were wounded in clashes between rival gangs, and youths blocked streets in the capital with burning tyres, officials said on Monday.

Four people were in critical condition requiring surgery after Sunday's violence, an official at the Dili national hospital said.

Gang violence is common in East Timor, an impoverished and young country of one million people.

Monica Rodriguez, a spokeswoman for the U.N. police in East Timor, said police backed by international troops fired tear gas and rubber bullets to disperse the crowd.

"They were burning rubber tyres and putting rocks and timber in the main streets in several areas," Rodriguez said.

Australian-led foreign troops and U.N. police were sent into East Timor following last year's wave of violence that left 37 people dead and 150,000 driven from their homes.

Major Ivan Benitez, a spokesman for the International Stabilisation Force, told reporters that officials were investigating an explosion at the main Australian military main compound at Dili heliport on Sunday night.

The explosion set ablaze a building there.

President Jose Ramos-Horta urged calm.

"I ask people not to dramatise the situation, because last night's incident was responded to quickly by police and based on information no one was injured or died," he said.

The violence came as rival parties in East Timor were negotiating the composition of a new government following the June 30 parliamentary elections.

"There's still no agreement on who is going to be prime minister and which party is going to lead the government," Ramos-Horta told reporters.

No party won more than half the vote in the parliamentary elections.

The president said last week that the ruling Fretilin party and an alliance led by ex-president Xanana Gusmao had agreed to form an all inclusive government, seen as crucial to heal deep divisions five years after independence from Indonesia.

But he also said he would have to step in to decide on a new government if parties could not reach an agreement.

The new parliament is due to be inaugurated on July 30.

AlertNet news is provided by