Italy has been accused of leaving hundreds of asylum seekers in parking lots on the suburbs of Rome and Milan without shoes, food or money.
The UN refugee agency said two groups of between 160 to 170 migrants from Syria, Somalia and Eritrea were abandoned near the two Italian cities after they landed in Sicily on Monday.
They were "found without shoes, disorientated, and without having been given anything to eat or drink," Carlotta Sami, UNHCR's spokeswoman in Italy told AFP. The two groups were shipped to Rome and Milan in coaches overnight. The ones left near Rome were eventually taken in by a centre for asylum seekers in the capital.
The refugees were part of a group of 1,300 migrants, including women and dozens of babies, who had been grabbed and taken to the southern Italian city of Taranto.
The UN High Commissioner for Refugees criticised the "unacceptable" treatment of the refugees.
Italy is struggling to deal with waves of immigrants washing up on its shores in overcrowded boats, with about 42,000 people who have attempted to cross the Mediterranean to the country's southern coasts, according to the EU border agency, Frontex. Last year the influx was 3,362 by the end of April, according to UNHCR.
Italy has vowed to force the migrant issue to the top of the EU agenda when it takes control of the presidency in July.
"During the European presidency, Europe will not see an Italy banging its fist on the table, but an Italy that overturns the table," interior minister Angelino Alfano said.