Malaysia is set to launch a large-scale operation against hundreds of thousands of illegal immigrants today.

The operation to round up, whip and deport illegal immigrants, mainly Indonesians, marks the end of an amnesty which has twice been extended at Jakarta's request.

Some 300 people from Myanmar, Cambodia and Indonesia's Aceh province lined up Monday at the UN High Commissioner for Refugees (UNHCR) hoping to secure UN support to remain in Malaysia.

Zaw Aung from Myanmar said he had been in Malaysia for 10 years illegally along with his wife and two children.

"With this crackdown, my friend who has been giving me shelter has told me to leave his house because he fears he may also be arrested. I have no home now. Please help me," he said.

Another Myanmar migrant, Morani, 32, had camped outside the UN agency for the past week with her four-year-old daughter to obtain a letter to prevent arrest or deportation.

"I am afraid of being arrested. We do not have any travel documents. We do not want to go back," she said.

Morani, whose husband works in the plantation sector in northeastern Kelantan state, said they had been in Malaysia for the past 12 years.

Malaysia is deploying tens of thousands of volunteers and officials to hunt down the illegal immigrants.

"We know many of the illegals have gone into hiding," Mahadi Arshad, director general of the 300,000-strong civilian security force volunteers, told AFP.

Mahadi said they would launch their blitz from late Monday. "We know where they are hiding."

Some 35,000 volunteers who have received special training would be involved in the operation along with hundreds of immigration and police officials, he said.

The crackdown would be Malaysia's largest blitz to flush out illegal immigrants in three years. A similar nationwide sweep was carried out in 2002 following the end of a four-month amnesty program.

The operation has been criticised by human rights groups which say it is open to abuse.

Amnesty International earlier this month urged Malaysia to halt the planned deportation of illegals amid fears some could face execution or torture in their home countries.

Migrants from Myanmar, Nepal and Aceh could be subjected to serious human rights violations if they were sent home in the crackdown, it said.

Before the recent amnesty began on October 29 last year, Malaysia estimated there were more than a million illegal workers in the country, mostly from Indonesia but also from the Philippines, Myanmar, Bangladesh, India and Sri Lanka.

Nearly 400,000, mostly Indonesians, left without facing any penalty during the first three months of the amnesty, but others have remained, clinging to jobs in the construction, plantation and service industries in the face of unemployment at home. Outside the Indonesian mission, hundreds of illegals were waiting with their luggage for buses to transport them to Port Klang, west of here to board an Indonesian navy ship.

"I came to Malaysia legally but my boss did not pay my salary for seven months. So I decided to run away from the company and worked illegally as a rubber tapper for the past three years," said Rahim, 21, from central Java.