Officials in Libya say more than 250 migrants, including women and children, have been rescued while trying to reach Italy.
The North African country's western shores remain a main departure point for those trying to get into Europe, though numbers have dropped dramatically since July.
"Yesterday night we moved from the city to the sea to go to Italy by boat, and we spent about 16 hours, but we could not get anywhere," one man said.
The migrants were later reportedly taken to a naval base in Tripoli.
The welfare of those trying to flee Libya for Europe has become a major cause of concern.
Amnesty International has accused European governments of being complicit in grave human rights violations by helping Libyan authorities to intercept people crossing the Mediterranean.