Dili – The head of the UN mission in East Timor on Monday branded Indonesian attempts to disarm pro-Jakarta militias as "pathetic" after two UN observers fled a militia riot at a West Timor police station.

Indonesia's top security minister, Susilo Bambang Yudhoyono, said on Monday the East Timorese militias terrorising West Timor have until Wednesday to give up their guns or police and soldiers would take them by force.

But UN mission chief Sergio Vieira de Mello told reporters in Dili Sunday's riot after a weapons handover in the West Timor town of Atambua attended by Vice-President Megawati Sukarnoputri proved only tough action would work against the militias.

"I personally never took the ... persuasive phase seriously," he said. "I do not believe that the militia will voluntarily surrender their weapons – and if they did, they would probably surrender the old rotten ones and keep the modern ones. What happened yesterday was pretty pathetic but not a surprise."

Rampaging militiamen slaughtered three foreign UN aid workers in Atambua three weeks ago, outraging the international community and stoking demands for Indonesia to disarm and disband the gangs.

Vieira de Mello said the UN observers fled to East Timor under heavy Indonesian military escort after followers of notorious militia leader Eurico Guterres rioted at the handover at the Atambua police station, many taking their weapons back. The police did nothing to stop the rioting, but locked the UN pair in a room inside the station for their own protection.

Guterres, who holds a key security position with Megawati's own party, abused police and kicked over chairs and furniture after being told Megawati and senior government officials had left without meeting him.

Several of his supporters made threats to the police about the safety of the two UN observers. "The mere fact that despite the presence of Vice-President Megawati in town, of the coordinating minister for security and political affairs [Yudhoyono] and senior TNI [military] and POLRI [police] officials, Mr Guterres could perform in his usual manner at the very headquarters of the Indonesian police in Atambua casts doubt on the ability of the Indonesian authorities to bring the militia under control," Vieira de Mello said.

Indonesia's plan is to persuade the militias to give up their weapons, followed by what it calls a "repressive" phase of enforcement from Thursday. "After that, any possession of weapons will face legal sanctions," Yudhoyono said, adding security forces would begin seizing weapons on Thursday.

Some East Timorese militiamen have started handing over weapons, in a move Jakarta hopes will help calm international anger over the murder of the UN aid workers.

The United Nations Security Council has demanded the militias be disarmed and disbanded and the United States has warned desperately needed aid could be at risk if Indonesia's wayward military did not bring the gangs under control.

Vieira de Mello said the real test of Indonesia's credibility would be what action it takes to break up the militias. "I'll be briefing the [UN] security council on Friday and by then we shall have a clearer idea on whether repression has been more effective, as I always thought, than persuasion."

[An Associated Press report on the same day said that no more weapons had been surrendered since September 24. A gang member, who spoke on condition of anonymity told AP that "Some of us have fled to the hills with our guns" – James Balowski.]