A military commander overseeing Indonesian West Timor has ordered his men to shoot on sight any armed militiamen found trying to cross the border with independent East Timor.

The order came from Major General Agus Suyitno, the state Antara news agency reported late Sunday.

"If you find any former East Timorese refugee or militiaman crossing the East Nusa Tenggara [West Timor]-East Timor border by carrying a weapon, you are justified to shoot him or her," Suyitno was quoted as telling his troops near the border.

United Nations peacekeeping troops in East Timor have said the well-trained groups of pro-Indonesian former militiamen pose a "real threat" to security in parts of East Timor.

Hundreds of UN troops were deployed to hunt down a group which attacked a bus on February 24 in a border district, killing two people. Four people have been arrested and appeared in court in Dili. Suyitno said another six people suspected of involvement have been arrested in West Timor.

In January attackers killed five people including independence supporters, also in the west of East Timor.

East Timorese officials have blamed both attacks on anti-independence militiamen seeking to destabilise the new country. They say they do not believe that former ruler Indonesia or its military chiefs were behind the infiltrations.

Suyitno said Indonesian security authorities were questioning six men suspected of being behind the February border shooting. He said they were arrested in the Belu district of West Timor on March 14-15.

"They are being intensively questioned and if it is clear that they are the perpetrators of the violence in East Timor, we are ready to help and hand over the suspects to the concerned authorities in East Timor as long as a demand for that is made through the proper procedures," Suyitno said.

UN Secretary General Kofi Annan has called for the peacekeepers' phased withdrawal to be slowed down to cope with the upsurge in violence by pro-Indonesian former militias.

Thousands of militiamen and their families fled to West Timor after foreign peacekeeping troops arrived in East Timor in September 1999 to halt a wave of militia violence following its vote for independence from Jakarta.