At least 40 migrants died in the hold of a boat off Italy Saturday as the EU struggled to cope with "the worst refugee crisis since World War II", with thousands making dangerous crossings to reach Italy and Greece.

"Operation under way... many migrants saved. At least 40 dead," the Italian navy said on Twitter, while the Corriere della Sera newspaper said those who died were found in the hold of the vessel, apparently having suffocated below deck.

Fighting between Islamic State group jihadists and rival gunmen in Libya's coastal city of Sirte has left dozens dead and wounded this week, a local official said on Friday.

The clashes erupted on Tuesday as authorities in the militia-held capital Tripoli, opposed to the internationally recognized government, announced the launch of an operation to retake Sirte from IS.

Once thought dead and buried on the battlefields of Iraq, a muscular and militaristic "neoconservative" approach to U.S. foreign policy is making a comeback.

For most of the last decade, the "neocons" -- personified by former vice president Dick Cheney and ex-Pentagon boss Donald Rumsfeld -- have been out of office and out of fashion.

Around 60 migrants are missing in waters off Libya, the International Organization for Migration (IOM) said Wednesday after interviewing survivors who were picked up from their stricken craft.

An Italian corvette, the Fenice, picked up dozens of migrants aboard a sinking rubber dinghy on Tuesday after the vessel was spotted by a naval helicopter.

The future of Libya's internationally recognized government was uncertain Wednesday after Prime Minister Abdullah al-Thani threatened to resign, and as the latest U.N.-brokered peace talks ended amid optimism about a deal.

Thani made the resignation threat during an emotional live television appearance in which he faced a barrage of angry questions from citizens, but it was unclear whether he planned to follow through.

A Libyan official visited a prison in rebel-held Tripoli on Monday to meet detainees including a son of slain dictator Moammar Gadhafi, after claims that he was ill-treated in jail.

The visit by Mustafa al-Kulaib, justice minister in the Tripoli-based government, comes after Human Rights Watch called for a probe into reported abuse of prisoners at Al-Hadba prison.

A car bomb attack claimed by the Islamic State group has killed nine people and wounded dozens in Libya's eastern coastal city of Derna, a medical source said.

"Nine persons were killed and dozens wounded in a car bomb in Derna city" on Sunday night, a medical official in eastern Libya told AFP by telephone.

Knife-wielding traffickers sealed migrants in the hull of a boat which sank off Libya, condemning them to drown after slashing or thrashing them depending on their ethnicity, according to survivor testimony reported Friday.

Italy has arrested five men accused of multiple murders and human trafficking following Wednesday's shipwreck, which left more than 200 people feared drowned.

Survivors of a shipwreck off the coast of Libya in which some 200 migrants were feared drowned arrived in Sicily on Thursday, as tales emerged of the "horrific" moment the boat overturned.

Their fishing boat, believed to have been carrying more than 600 people, ran into difficulty about 15 nautical miles off Libya on Wednesday and tipped over when rescuers neared, after frantic migrants rushed to one side in their desperation to be saved.

The EU attacked member states Thursday for not doing enough to halt the flow of migrants to its southern shores, saying regret at the latest deaths was no substitute for action.

"Migration is not a popular or pretty topic. It is easy to cry in front of your TV set when witnessing these tragedies. It is harder to stand up and take responsibility," top EU officials said in a statement.