But Home Minister Azmi Khalid said the government would go ahead with the plan as it had given the migrants the chance to leave the country voluntarily during an amnesty which expires at the end of this month.

"As for illegals, if they are scared of being harassed then don't be an illegal," he told a news conference. "We gave you an amnesty. Of course, we try and tell our (enforcement) people please be kind."

But Amnesty echoed concerns already expressed by Human Rights Watch and the UN refugee agency that the mass expulsion could lead to abuses, including the deportation of genuine refugees who face persecution in their own countries.

"Our fear is real. Abuses have happened previously," Josef Roy Benedict, local campaign coordinator of Amnesty told AFP.

"Given the scale of the proposed 2005 detentions and deportations, Amnesty International fears that violations of the rights of the detainees may re-occur," the group said.

Adding to the concerns of the rights organisations is the fact that more than half a million members of volunteer neighbourhood security groups will be given the right to detain illegal migrants.

But Azmi said the civilian groups had sufficient experience and training to carry out the operation. "Don't use this as an excuse (to halt the plan). We want to give power to the people ... to empower the people," he said.

The United Nations High Commissioner for Refugees (UNHCR) office in Malaysia announced Wednesday that it would deploy mobile teams in an urgent effort to register refugees hiding in the jungles on the fringes of Malaysian cities where many work illegally.

It is feared that asylum seekers from military-ruled Myanmar and the strife-torn Indonesian province of Aceh will be swept up along with the illegal migrants, Volker Turk, head of the UNHCR in Malaysia told AFP.

There are an estimated 1.2 million illegal immigrants in Malaysia, mainly from neighbouring Indonesia and the Philippines but also from India and Bangladesh, who are drawn by jobs in construction, plantation work and services.

Malaysia has said it will move against the illegal migrants at the end of an amnesty, which began on October 29. The amnesty was originally designed to last 17 days, but has been extended until the end of this month at the request of the Indonesian government.