A boat packed with migrants sank off the Libyan coastal city of Zuwara on Thursday and officials said hundreds may have died.
A security official in Zuwara said several hundred people were on board and some appeared to have been trapped in the hold when it capsized.
“Some 100 illegal migrants have survived,” he said, adding that rescue operations were continuing.
Another local official and a journalist based in Zuwara confirmed the sinking but had no information on casualties. The migrants on board had been from sub-Saharan Africa, Pakistan, Syria, Morocco and Bangladesh, the security official said.
The Italian coastguard, which has been coordinating rescue operations by the European Union off the Libyan coast, could not immediately confirm a sinking.
Zuwara, near the Tunisian border, is a major launchpad for smugglers shipping migrants to the Italy.
More than 2,300 people have died this year in attempts to reach Europe by boat, compared with 3,279 during the whole of last year, according to the International Organisation for Migration.
As many as 50 refugees were found dead in a parked lorry in Austria near the Hungarian border on Thursday, and German chancellor Angela Merkel said the discovery had shaken European leaders discussing the migrant crisis at a Balkans summit.