The U.N. High Commissioner for Refugees has expressed alarm over the arrest of hundreds of refugees from Indonesia as they tried to apply for political asylum in Malaysia.

A spokesman for the U.N. High Commissioner says the agency was expecting up to 600 people to register as refugees at the agency's office in Kuala Lumpur. The people are from Indonesia's war-torn Aceh Province. Evan Ruth says Malaysian police set up roadblocks around the UNHCR office and intercepted the asylum seekers. Mr. Ruth says the asylum seekers, including women and children, were being held at a local police station.

"The secretary general of the United Nations has expressed his concern of the situation in Aceh and the effect the conflict is having on civilians," said Mr. Ruth, "and we believe that these civilian Acehnese must be protected and should not be returned to Aceh." He says Malaysia has not signed the U.N. convention on refugees, and does not differentiate between refugees and illegal migrants.

The UNHCR says it is alarmed by what it called the Malaysian government's "unprecedented action." The agency's statement says Malaysia previously had tried to respect the needs of refugees fleeing war. Mr. Ruth says the UNHCR is trying to ensure that the detainees will not be repatriated. "We are also intervening through our headquarters in Geneva at the very high levels of the Malaysian government to impress upon them the need to ensure that these people are not be returned to Aceh," he added.

In May, a peace accord between separatist rebels in Aceh and the Indonesian government collapsed, and fighting resumed. Mr. Ruth says since then the number of Acehnese seeking asylum in Malaysia has increased.

Rebels have been fighting for independence in the resource-rich province since 1975. More than 12,000 people have died during the conflict, most of them civilians. At least 600 people have been killed since May. International human-rights groups accuse the Indonesian military of committing many rights abuses. The military says the rebels are committing the abuses.