PARIS — The Tunisian authorities have recovered the bodies of 150 refugees, mostly sub-Saharan Africans, who drowned after their boat foundered this week in the Mediterranean Sea, a United Nations official said Friday, but up to 120 refugees were still missing.

“The authorities have managed to recover 150 bodies so far,” said Firas Kayal, a spokesman for the United Nations refugee agency in Tunisia. “The search operation is still going on.”

The clandestine migrants, aboard a 100-foot fishing vessel, had been fleeing Libya for Europe. Rescuers from the Tunisian Coast Guard and Navy were able to save 578 men, women and children from the vessel, which was crowded with as many as 850 passengers when it ran aground Tuesday about 30 miles from the Kerkennah Islands, said Col. Lotfi Baili of the coast guard, who helped coordinate the operation.

Hundreds of passengers fell from the vessel when it listed, he said, and others fell into the water during the scramble to reach the military rescue boats. The Tunisians were overwhelmed by the number of migrants who needed to be rescued, he said, and could use only small vessels because the water was so shallow.