(CNN) -- At least 94 people, including a pregnant woman and two children, died when a boat capsized and caught fire off the island of Lampedusa, the Italian coast guard told CNN on Thursday.
The coast guard has been able to save at least 151 people, and the rescue operation is ongoing.
The boat is thought to have been carrying up to 500 people. Those aboard include Somalis, Eritreans and Ghanaians, the coast guard said, and the boat is thought to have launched from Libya's coast.
Lampedusa, the closest Italian island to Africa, has become a destination for tens of thousands of refugees seeking to enter European Union countries.
The head of the U.N. refugee agency, Antonio Guterres, praised the efforts of the Italian coast guard but said he was "dismayed at the rising global phenomenon of migrants and people fleeing conflict or persecution and perishing at sea."
Another 13 men drowned off Italy's southern coast Monday when they attempted to swim ashore, the U.N agency said in a statement.
It is working with countries in the region to find "effective alternatives" so people don't risk their lives trying to make perilous journeys by sea, it said.
Lampedusa, a tiny island off the coast of Sicily, was in the news this summer when the pope went there to pray for refugees and migrants lost at sea.
"We pray to God for the victims of the tragic shipwreck in Lampedusa," Francis said Thursday on the Italian version of his Twitter account.
Just under 115 kilometers (70 miles) from Tunisia, the island has been the first point of entry to Europe for more than 200,000 refugees and irregular migrants who have passed through the island since 1999.
But boats carrying migrants often are in peril at sea.
In recent years, the Italian Coast Guard says it has been involved in the rescue of more than 30,000 refugees around the island.