Mark Dodd, Dili – Despite nagging security concerns, the United Nations gave its qualified approval yesterday to start voter registration in East Timor, less than six weeks before its planned vote on self-determination.

The UN Secretary-General, Mr Kofi Annan, told the Security Council in a letter that it was not possible yet to make a "positive assessment" of the security conditions throughout East Timor.

But he decided to allow voter registration to proceed from today throughout the territory and at external registration centres in Portugal, Australia, Indonesia, Macau, Mozambique and the United States, where there are large communities of Timorese exiles.

The UN will review security half way through the 20-day voter registration period, and it is still possible that the vote, already postponed once from August 8 to August 21 or 22 because of violence by pro-Indonesian militias and logistical delays, may be postponed again. The head of the UN Assistance Mission in East Timor, Mr Ian Martin, said strong assurances from the Indonesian Government that it would improve security territory-wide had been critical in the decision to proceed with voter registration.

But he warned that if Indonesia failed to make good its promise he would not hesitate to suspend voter registration.

Indonesia, meanwhile, mounted a new show of force in Dili. An Indonesian Air Force jet, one of three British-made Hawk 100 fighters based at Kupang in West Timor, made two low passes over the provincial capital, while a frigate appeared offshore. One diplomat described it as "macho posturing" to remind East Timorese who was controlling the territory.

Mr Martin's warning to Jakarta was backed up by equally strong comments from the US Assistant Secretary of State Mr Stanley Roth, arriving from Jakarta on a two-day visit.

"All the senior officials I met – President Habibie, [Defence Minister] General Wiranto – indicated to us they intended to abide by the terms of the New York [May 5] agreement," Mr Roth said.

"What we are looking for is the result on the ground. I think I made it clear [yesterday] there was enough significant evidence that elements of the military had been supporting some of the militia groups and that was a large contribution to the lack of security on the ground."

More than 200 people have been killed in militia violence since January and more than 60,000 people displaced, causing a major humanitarian crisis and a logistical nightmare for electoral staff.

Today, 200 voter registration sites staffed by 400 district electoral officers will open across the half-island territory to register an estimated 390,000 eligible voters. Registration was delayed by three weeks last month and again for three days last week because of security worries.

Mr Martin welcomed an announcement by the Indonesian police that six members of a pro-Jakarta militia had been arrested over an attack last month on a UN office in south-west Maliana.

Another seven men suspected of being members of the hardline Besi Merah Putih (Red and White Iron) militia had been arrested and were being held in police custody in Dili for their alleged involvement in an attack on a humanitarian convoy in western Liquica earlier this month.