"So far, there are no changes to our policy, we will begin the operations on February 1," Home Minister Azmi Khalid said.

Malaysia has announced that it will deploy more than half a million members of volunteer security groups along with police to track down and detain illegal immigrants, mainly from Indonesia, Myanmar and the Philippines.

Several rights groups have criticised the move, with Amnesty International saying it could lead to abuses and Human Rights Watch describing it as "ominous".

But Azmi sought to allay fears saying that the volunteers had undergone training and were familiar with operational procedures.

"We have instructed them to act in accordance with their given authority. None of our people have ever used force against these illegals. In fact we fear that the illegals will use force against our officers," he was quoted as saying by the official Bernama news agency.

All the logistics had been prepared, including transportation, handcuffs and batons, as well as all detention camps around the country which can hold up to 16,000 detainees at any one time, he said.

A memorandum issued by the rights group Voice of the Malaysian People (SUARAM) on Saturday urged the government to halt the crackdown amid concerns that asylum seekers and victims of human trafficking would be detained together with illegal immigrants.

"Forced deportation of these vulnerable groups (asylum seekers and refugees) is in breach of international customary law, putting them at risk of serious human rights violations, including extrajudicial executions, torture, arbitrary detention and 'disappearances'," said the memorandum, which was endorsed by 39 other non-governmental organisations.

"There is high potential for human rights abuses to occur through such mass-scale operations," it warned.

The government has twice extended an amnesty for an estimated 1.3 million illegal workers to leave the country, firstly at Indonesia's request and then again after the tsunamis hit the Indonesian province of Aceh on December 26.

Indonesians make up the bulk of the illegal workers in Malaysia, many of them from Aceh. Nationals from tsunami-hit India and Sri Lanka also work illegally in Malaysia, drawn by jobs in the construction, plantation work and service industries.

Some 320,000 illegal workers are reported to have taken up the offer to return home without penalty since the amnesty began in October.