Six bodies were recovered from the sea after a wooden migrant boat carrying about 35 people capsized off the coast of Libya, the UN said on Saturday.
More were feared dead.
The capsize incident was on Friday off the western Libyan city of Sabratha, the International Organisation for Migration said.
The IOM said that 29 others were missing, presumed dead.
In the past week, at least 53 migrants have been reported dead or missing off the coast of Libya, it said.
The IOM has described Libya as a springboard for people fleeing war and poverty in the hope of reaching European countries for shelter and opportunity.
"I am appalled by the loss of life in the central Mediterranean and the lack of action to tackle this tragedy,” Federico Soda, IOM Chief of Mission in Libya, said last month after more than 70 people were reported missing.
