A joint statement by the interior ministers of the four countries said they had agreed to set up centres in Chad and Niger, key countries of transit for migrants who travel to Libya and on to Italy from sub-Saharan Africa.
The statement, released on Sunday after an Italy-organized meeting in Rome, said the new centres in Chad and Niger, and the existing ones in Libya, would live up to "international humanitarian standards".
Rights groups have slammed the conditions of existing detention centres in crisis-hit Libya and questioned how the West can ensure such "international standards" are met and kept.
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"Libyan legislation criminalizes illegal immigration so it is not clear how these could be reception centres and not detention centres," Mattia Toaldo, a European Council on Foreign Relations expert, said on Monday.
"The establishment of 'reception centres' in Niger and Chad is also questionable: is Europe outsourcing its border control to these countries? If so, in exchange for what amounts of money and coming from where?".
Toaldo also questioned why the deal was made by interior ministers and how they hoped to follow through on a commitment to "promote legal economic development" as an alternative to the wealthy trafficking trade.
Brink of famine
On Sunday the head of the United Nations refugee agency Filippo Grandi urged Libyan authorities to free all asylum seekers and refugees from its detention centres, slamming the conditions as "shocking".
While promising to try to step-up the UNHCR's presence, Grandi said it would take time for political and security reasons. Libya has long been a stepping stone for migrants seeking a better life in Europe. People smugglers have stepped up their lucrative business in the chaos which has engulfed the country since its 2011 revolution.
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Italy registered nearly 50,000 migrant arrivals by sea by mid-April, 97 percent of them from Libya, according to Rome, and the country's own migrant centres have become overcrowded.
Nigerians have made up the largest group of people fleeing for Italy since January. Two million people are teetering on the brink of famine in the country's northeast, home to the notoriously ruthless Boko Haram.
The jihadist group launched an uprising there in 2009 which has since spilled over into neighbouring Chad and Niger.