More than 700 migrants may have drowned in the Mediterranean Sea south of Italy in the past few days as they tried to reach Europe, the UN refugee agency said.
Carlotta Sami, spokeswoman for UNHCR, said an estimated 100 people are missing from a smugglers' boat that capsized on Wednesday.
She said about 550 others are missing from a smuggling boat that capsized on Thursday morning.
Refugees said that boat, carrying about 670 people, did not have an engine and was being towed by another smuggling boat before it capsized, Ms Sami added.
About 25 people from it survived, 79 others were rescued by patrol boats and 15 bodies were recovered.
Ms Sami said 45 more bodies were recovered from a shipwreck on Friday and many more are reported missing.