More than 200 asylum seekers have drowned off the coast of Libya within 48 hours, the United Nation's refugee agency said.

Five rescue ships, coordinated by the Italian coastguard, were within sight of the asylum seekers but, despite attempts to rescue them, most died, the International Organization for Migration's (IOM) chief spokesman, Leonard Doyle said.

The latest incident takes the death toll in the Mediterranean to 4,220 migrants so far this year, compared with 3,777 for the entirety of 2015.

Asylum seekers have told the refugee agency that smugglers say European training of Libyan coastguards means that rescue missions will soon be handed over to Libya and so any rescued migrants will be taken ashore in Libya rather than in Italy, IOM's Italy spokesman Flavio di Giacomo said.

That might be causing the rush, despite the bad weather, he said.

Migrant and refugee arrivals in Italy increased to 27,388 in October, more than the two previous Octobers combined, and bringing this year's total to more than 158,000, Mr Giacomo said.

According to Mr Doyle, the use of dinghies, especially unsuitable for the long sea crossing in bad weather, was partly due to European navies capturing and destroying many of the fishing boats that smugglers had been using.

"In the absence of those boats and with the migrants determined to leave, and the smugglers interested in making money off them, they have been putting them in completely unsafe rubber dinghies," he said.

Survivors from one dinghy, whose passengers included about 20 women and six children, said their boat sank within hours of leaving Libya.

Twelve bodies, including three babies, have been recovered and about 27 survived, Mr Giacomo said.

Another two women said they had survived the sinking of a second dinghy, carrying about 130 people.

Separately, Italy's coastguard 766 people were rescued from boats in difficulty in the central Mediterranean on Thursday, one woman's body was recovered.

Reuters