At least 239 migrants have drowned in two shipwrecks off the coast of Libya on Thursday, while during the same day rescuers saved more than 760 survivors in a series of operations.

Rescue vessels coordinated by the Italian Coast Guard brought survivors of the shipwrecks, the majority of whom are from the African nation of Guinea, to the Italian island of Lampedusa.

Two rubber dinghies carrying hundreds of African migrants capsized in heavy seas not long after leaving Libya. The first dingy, with some 140 migrants aboard, capsized about 25 miles off the Libyan coast, according to the UNHCR. Of these, 29 survivors were rescued and 12 bodies were recovered.

The second dinghy was carrying around 130 people, almost all of whom drowned shortly after their vessel capsized.

The migrants had spent almost two months in a dormitory in Libya before being brought to the coast and taken by force onto the boats, despite the poor sea conditions and the fact that one of the two boats was clearly defective.

Carlotta Sami, spokesperson for the UN refugee agency (UNHCR), reported the news in a series of tweets.

In 7 different international rescue operations Thursday, the Coast Guard, aided by a number of other organizations, saved 766 migrants in the central Mediterranean. Meanwhile, authorities arrested 11 suspected smugglers in Messina. The alleged traffickers are from different countries of central Africa and are accused of aiding illegal immigration.

Thursday’s deaths have brought this year’s toll to more than 4,220 migrants dead or missing, mostly in attempted crossings of the perilous Strait of Sicily that separates Italy from North Africa. The number of Mediterranean sea deaths for this year has already surpassed last year’s, and is the highest yearly count on record.

UNHCR reported that the increased number of deaths this year is due in part to the fact that traffickers are often resorting to precarious rubber dinghies rather than sturdier vessels to make the crossing. The shift from Greece to Italy as the prime point of entry into Europe has also raised the stakes, since the trip across the Strait of Sicily is far longer and more dangerous than the relatively short journey from Turkey to several of the Greek islands.

Last year, 3,777 people died or went missing as attempting to cross the Mediterranean last year, which was the previous high.

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