Human Rights Watch on Sunday urged Israel to repeal or amend a law that allows migrants to be detained without charge for up to three years, calling it a violation of "basic rights."
The New York-based group said the new law "punishes asylum seekers for irregularly crossing into Israel, in violation of their basic rights."
"Subjecting irregular border-crossers to potential indefinite detention without charge or access to legal representation would violate the prohibition against arbitrary detention under international human rights law," it said.
Israel announced on June 3 that officials would be able to detain migrants who crossed into the Jewish state illegally for up to three years, as part of a bid to stem the flow of African migrants into the country.
But Human Rights Watch said the law stood to stoke anger against migrants, which erupted last month when a protest by around 1,000 people against the rising number of Africans in Israel turned violent.
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"Israeli officials are not only adding rhetorical fuel to the xenophobic fire, but they now have a new law that punishes refugees in violation of international law," said Human Rights Watch's refugee programme director Bill Frelick in a statement.
"The law should be amended immediately, and not enforced until necessary revisions are made."
Interior ministry statistics show there are approximately 60,000 African immigrants who have entered Israel illegally. Some are refugees fleeing persecution in their home nations, but others are economic migrants.
During the protest last month, demonstrators went on the rampage, attacking African-run shops and smashing up a car driven by two African men.
Police said afterwards that 20 people had been arrested on suspicion of vandalising shops and attacking cars driven by Africans, but there were no injuries.
Migrants have subsequently been targeted in several attacks, including the firebombing of an apartment in Jerusalem last week.
The riots sparked shock in Israel, but also prompted top-level calls for the immediate arrest and expulsion of tens of thousands of African migrants, most of whom come from Sudan, South Sudan and Eritrea.