The Voice of the Malaysian People (Suaram) said 93 ethnic Chin asylum seekers were among the group, which also included migrants from Bangladesh, India, Indonesia, Nepal and Vietnam.

"Suaram deplores the indiscriminate act and the raid on the Chin Refugee Center that has been deliberately directed against those coming to find a safe haven from political turmoil and poverty," said executive director Yap Swee Seng.

Yap said the migrants, including 27 women, were being held in the overcrowded Lenggeng detention camp in Negeri Sembilan, south of Kuala Lumpur.

"Suaram is concerned over prospects of prolonged detention under such deplorable conditions and potential deportation of detainees to their countries of origin where their lives will be in serious danger," he said.

Malaysia since 1992 has launched several operations against illegal workers, most of whom come from impoverished parts of Southeast Asia.

But each one has led to a labour shortage followed by a new wave of illegal immigration -- a pattern which was apparent after a blitz last year.

Malaysia is one of the largest importers of foreign labour in Asia. Foreign workers, both legal and illegal, number around 2.6 million of its 10.5 million workforce, officials say.