Human Rights Watch has warned that Malaysia's plan to arrest and deport hundreds of thousands of illegal immigrants could spark rights abuses and harm legitimate refugees and victims of human trafficking.

The expulsion plan "may result in widespread rights abuses," the New York-based Human Rights Watch said in a statement released Tuesday.

The rights group fears that police may use excessive force during immigration raids, and that detainees could end up for long periods in overcrowded, unsanitary camps.

"Refugees and victims of human trafficking may be caught up in the sweeps and deported instead of receiving protection," the statement said.

Malaysian authorities plan to launch the crackdown following an amnesty period that allows illegal immigrants to leave the country without being detained. The amnesty is expected to end next month.

Undocumented workers face prison sentences of up to five years, fines and whipping with a rattan cane if convicted under Malaysian immigration laws. About 9,000 offenders were whipped last year, Human Rights Watch said.

Malaysia has about 28,000 refugees, most of whom are from Indonesia's war-torn Aceh province or are members of Myanmar's Rohingya ethnic Muslim minority, who've long accused their country's predominantly Buddhist military of persecution.

Officials estimate some 1 million illegal immigrants work in Malaysia's construction, plantation and domestic services sectors, mostly from Indonesia but including many from the Philippines, India, Bangladesh and other Asian countries.

More than 80,000 illegal immigrants have so far left under the amnesty program.

The group also urged the Malaysian government to scrap a plan to reportedly allow 400,000 civilian members of volunteer neighborhood security watch organizations to help conduct immigration raids, saying the plan "encourages vigilantism and undermines the rule of law."