Rescue ships including vessels from the Italian and Irish navies and humanitarian agency Medecins sans Frontiers (MSF) recovered 25 bodies after the boat sank off the Libyan coast on Wednesday and found no more overnight, a spokesman said.

Initial reports put about 700 passengers on the overcrowded steel-hulled boat but interviews with survivors - mostly Syrians fleeing their country's civil war - reduced that estimate and the figure could still change.

Another large migrant boat was spotted in the area yesterday, just 30 miles from the Libyan coast, and one of the Italian rescue ships was sent to its aid, the spokesman added.

The capsized boat flipped over yesterday as a rescue vessel approached, probably because desperate passengers surged to one side as they saw help arrive. "We don't know how many people might be trapped within the belly of the boat that capsized and sunk, that's our greatest fear tonight," MSF, whose Dignity 1 rescue ship was on the scene, said in a Tweet yesterday.

"People were clinging to life rafts, fighting for their lives," cited MSF's Juan Matias, who was aboard Dignity 1. The Mediterranean Sea has become the world's most deadly border area for migrants.

More than 2,000 migrants and refugees have died so far this year in attempts to reach Europe by boat, compared with 3,279 deaths during the whole of last year, the International Organization for Migration said.

Latest News from World News Desk