Survivors said that several dozen migrants were unaccounted for and were feared to have drowned.
The boats were at sea near Garabulli, where departures have become more common since local armed groups began preventing boats from leaving from the coast to the west of Tripoli last summer.
Slightly fewer than half as many migrants reached Europe by sea in 2017 than 2016, according to the International Organization for Migration (IOM), largely because of a drop in crossings between Libya and Italy.
The IOM said that nearly 120,000 migrants docked in Italy over the course of last year, out of a total of more than 171,500 who arrived in Europe by sea, mostly fleeing war in the Middle East and poverty in Africa.
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