TRIPOLI, Libya — The Libyan Navy said on Wednesday that its Coast Guard had rescued at least 279 migrants off the coast of Libya, but that about 100 more were missing and feared dead.

The migrants, mostly Africans, had been packed into several vessels hoping to cross the Mediterranean and reach southern Europe. The missing appeared to have all been in the same dinghy, whose remnants were found near the city of Khoms, the navy said.

Search-and-rescue efforts continued for more than 12 hours in rough conditions, the navy said. All of the survivors, including 19 women and 17 children, were taken to a naval base in the capital, Tripoli, and were later handed over to Libya’s anti-migration authority.

The United Nations migration agency estimates that more than 3,100 migrants died while trying to cross the Mediterranean in 2017, a number attributed to smugglers’ use of small dinghies and other poor-quality vessels.