At least 116 migrants are missing and another 132 were rescued by Libyan coast guards and local fishermen after a wooden boat capsized off the coast of Komas, a town east of the capital Tripoli, a Libyan navy spokesperson said on Thursday.
Ayoub Qassem cited survivors as saying there had been more than 200 migrants on board the boat.
Earlier, the UN refugee agency UNHCR said up to 150 people were feared dead in the shipwreck and another 150 were rescued.
UNHCR and other UN agencies have repeatedly called for survivors not to be returned to Libya, a conflict zone where rescued migrants and refugees are routinely jailed in inhumane conditions.
The ship reportedly left Libya from Al Khoms, a town 120 kilometres east of Tripoli.
The survivors were picked up by local fishermen and returned to the coast by the Libyan coastguard, UNHCR spokesperson Charlie Yaxley said.