Hundreds feared dead after a boat packed with migrants sinks off Libyan coast.
A security official in the coastal city of Zuwara said there were several hundred people 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 were 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.
On Wednesday, the Irish navy vessel LÉ NIAMH rescued more than 500 migrants less than 55 km north of Zuwarah.