Jose Sousa-Santos, an adviser to Prime Minister Jose Ramos-Horta, said much of last week's fighting in the capital Dili was due to the use by youth gangs of locally-made methamphetamine, or "ice," which can trigger uncontrolled rages.
"It's more a pre-battle ritual," he told Australian media. Sousa-Santos said the methamphetamine had only appeared in Dili since fighting broke out between the police and military in May.
Local officials said two people were killed in the clashes last week between youths armed with guns, rocks and bows and arrows. But Australia, which is leading a peacekeeping force in the fledgling nation, said the toll was six dead and 50 injured.
"We are concerned that this violence may be organised in some instances for what might broadly be described as political reasons," Australian Foreign Minister Alexander Downer told parliament in Canberra. The commander of Australian peacekeeping forces in East Timor, Brigadier Mal Rerden, said alcohol or ice aggravated two days of clashes, which shut down Dili's main airport.
"This is unfortunate -- they may do things they normally wouldn't do, and that is a dangerous and serious thing," Rerden told Australian newspapers.
Australia led a force of more than 2,500 regional soldiers and police into Dili in late May to end instability that eventually forced the resignation of Prime Minister Mari Alkatiri.
The Australians were met with cheers when they arrived and Prime Minister Jose Ramos-Horta this month turned down an offer of a UN replacement force, opting to keep Australian and New Zealand forces instead.
But security forces now suspect unknown figures of running a clandestine campaign against the Australian presence in hopes of forcing their departure ahead of national elections next year.
Acting Timor Prime Minister Estanislau da Silva said he was determined to crackdown on a nascent campaign aimed against the Australians, including allegations they were involved in the deaths of two youths last week.
"We will do our best to find out who is behind this campaign that has made people turn suddenly against the Australian force," da Silva told Fairfax newspapers.
Downer said Canberra suspected the violence was linked to a United Nations report into the May violence, which called for prosecutions of East Timorese leaders behind the clashes.
But Australia's 1,000 troops would stay in the country as long as they were needed, he said. "We'll remain committed to the task in East Timor through to the general elections, which are scheduled to be in May 2007, and no doubt beyond," Downer said.

Copyright Reuters, 2006