Two migrants drowned and at least another one is missing after a fishing boat crowded with almost 200 migrants ran aground off Pantelleria this morning.

The boat, carrying migrants from Somalia, was heading towards a bay on the Italian island when it drifted onto the rocks in heavy seas, according to media reports. A rescue operation is under way.

Those on board the boat included 11 women and six children. The boat is thought to have left from Libya.

"In addition to the two women who died, there is a third person whom police gunboats failed to recover," said Pantelleria mayor Alberto Di Marz, quoting the coast guard and police.

Passengers were thrown into the sea and then had to swim ashore, according to the ANSA news agency.

ANSA said police arrested the presumed smuggler who piloted the boat.

Italy is struggling to cope with a mass influx of immigrants from north Africa, many of whom risk their lives by sailing across the often stormy Mediterranean in makeshift vessels.

Around 150 people are feared to have been killed last week after their boat capsized in heavy seas off the Italian island of Lampedusa after they had set sail from Tunisia.