Hundreds of people are feared dead after two boats carrying about 500 migrants sank off Libya, officials say, the BBC reports.
The first boat, which capsized early on Thursday, had nearly 50 people on board. The second, which sank later, was carrying about 400 passengers.
A Libyan official told the Reuters news agency that about 200 people had been rescued but this is unconfirmed.
The UN says about 2,400 migrants have died trying to cross the Mediterranean to Europe so far this year.
More than 100,000 others have landed in Italy, whilst another 160,000 have crossed to Greece.