About 5,000 refugees bound for Italy were rescued in waters off the coast of Libya between Thursday and Saturday morning by Italian and Libyan coastguards, according to statements from both countries.
About 2,900 people were rescued on Thursday, 2,300 of whom were found in international waters and taken to Italy, while 580 picked up in Libyan waters were returned to the north African country.
Through Friday until Saturday morning, coastguards rescued another 2,100 refugees packed in 17 vessels, but found the body of one man who drowned, the Italian coastguard said.
The surviving refugees told the Reuters news agency of arbitrary detention, slavery and beatings in Libya.
"Libya is crazy. They arrest us, the police... They put us in some place... two, three days no eat, no drink. They beat us," said Alseer Issa Ibrahim, 28, from the Darfur region of Sudan.
John Osifo, a 29-year-old Nigerian, spent 11 months in Libya. He said he did not plan to go to Europe, but after a few months working at a car wash, a local man destroyed his passport and work permit, making him an irregular migrant, and he was forced into hard labour.
In Libya "they believe blacks are slaves. That is what they call us. When they want to beat us, they beat us with pipes," he said, showing a scar on his left hand.
"They take us to jobs, force us to do hard labour without payment ... Sometimes they take you to a prison where you'll be kept and beaten up," he said.
The number of refugees arriving in Italy has soared this year by more than 30 percent in comparison with the same period last year, with 46,000 people arriving so far.
But of every 39 refugees who survive the perilous journey across the Mediterranean, one dies, the International Organisation for Migration (IOM) said, adding that 1,244 refugees were known to have died so far this year.
Italy has become the hardest-hit European destination for refugees from Africa this year.
The UN High Commissioner for Refugees has estimated that, of the 55,000 people who have reached Europe this year, 83 per cent of them went to Italy.