Sydney – Rebel leader Jose Alexandre Gusmao should be released from Indonesian custody and allowed to take part in the ballot on East Timor 's future, United Nations special envoy Jamsheed Marker said Friday.

"We think it is important that Xanana be allowed to return to East Timor and allowed to work there," Marker told reporters, calling Gusmao, also known as Xanana, a "force for reconciliation. It is important that he participate," Marker said.

Gusmao is serving a 20-year sentence under house arrest in the Indonesian capital, Jakarta. He was arrested in November 1992 and sentenced in 1993 to life for leading an uprising against Indonesia. His sentence was later reduced. The Indonesian government has said that his release could only come as part of a "total solution" to the East Timor problem.

Tension is increasing in the former Portuguese colony ahead of the UN-sponsored ballot on autonomy or independence for East Timor scheduled for later this month. Indonesia invaded the half-island territory in 1975 and annexed it the following year.

One UN worker has been attacked and others evacuated from offices in areas outside the capital, Dili.

In the latest unrest, a UN spokesman said Friday six members of the UN Assistance Mission were evacuated from Liquicia, a stronghold of anti-independence sentiment and the site of atrocities against civilians in recent months.

Marker, in Australia after touring East Timor and attending talks between rival factions in Jakarta, said the security situation was still unsuitable for a free and fair vote, but it is improving.

The UN agreement specifies that Indonesia establish security in the region for the ballot to be free and fair.

Marker blamed "hooligans" for the threats against UN personnel, and said more could be expected before the vote. "It goes with the territory," he said.

The hooligans were acting without the authority of Indonesia's top military commanders, but the involvement of local officers could not be ruled out, Marker said.

"Law and order has not been restored as fully as we would want it," Marker said. "But I am satisfied with the bona fides of the Indonesian government in trying to bring this situation around."