GENEVA: An estimated 90 migrants are feared to have drowned off the coast of Libya after a smuggler's boat capsized early on Friday, leaving three known survivors and 10 bodies washed up on shore, the International Organisation for Migration (IOM) said.

Survivors told aid workers that most of the migrants on board were Pakistanis, who form a growing group heading to Italy from North Africa, IOM spokeswoman Olivia Headon, speaking from Tunis, told a Geneva news briefing.

"They have given an estimate of 90 who drowned during the capsize, but we still have to verify the exact number of people who lost their lives during the tragedy," she said.

Earlier security officials in the western Libyan town of Zurawa said two Libyans and one Pakistani had been rescued from the boat. It said 10 bodies had been recovered, mostly Pakistani, but gave no further information.

Zurawa, located near Libya's border with Tunisia, is a favoured site for migrant boat departures .

Libya is the main gateway for migrants trying to cross to Europe by sea, though numbers have dropped sharply since July as Libyan factions and authorities - under pressure from Italy and the European Union - have begun to block departures.

More than 600,000 people are believed to have made the journey from Libya to Italy over the past four years.