The Italian navy said it pulled to safety the survivors of the shipwreck and recovered seven bodies. The rescue was ongoing amid fears the death toll could rise.
An Italian navy patrol vessel rushed to the scene with lifeboats and life-jackets after spotting a the boat just before it overturned “due to the high number of people on board,” the navy said.
Some 5,600 people were rescued from the Mediterranean on Monday and Tuesday alone in 38 separate operations, Italian coastguard said
The latest arrivals bring to nearly 40,000 the number of people plucked from the sea and brought to Italy since January, the United Nations refugee agency (UNHCR) said earlier this week.
The number of arrivals is broadly stable from the same period last year while the number of people who died crossing the Mediterranean – 1,370 – fell by almost a quarter, the International Organization for Migration (IOM) said on Tuesday.
No breakdown of the nationalities of the people rescued was immediately available but the vast majority of those reaching Italy so far this year have been from sub-Saharan Africa.
Officials say there is no sign yet of Middle Eastern refugees switching to the Libyan route to Europe following a deal to restrict access from Turkey via the Greek islands amid the ongoing crisis.
Some 1.1 million refugees and migrants arrived in Europe last year, seeking refuge from war and poverty in the Middle East, Africa and Asia.