Divers are battling with choppy waters in the search for dozens of migrants believed to have drowned after their rickety boat caught fire and sank off the coast of the southern Italian island of Lampedusa.

The scope of the tragedy -- with 111 bodies recovered so far and as many as 200 missing - prompted outpourings of grief and demands for a comprehensive immigration policy to deal with migrants fleeing poverty and strife in Africa and the Middle East.

Pope Francis said Friday was a "day of tears" and denounced the "savage" system that drives people to leave their homes for a better life, yet doesn't care when they die in the process.

Officials say just 155 people survived of the 450 to 500 believed to have been on board.

It was one of the deadliest recent accidents in the perilous Mediterranean crossing that thousands of African migrants make every year, seeking a new life in the European Union. Smugglers charge thousands of dollars a head to slip people into Europe aboard overcrowded, barely seaworthy fishing boats, providing no life vests or other safety features.

According to Interior Minister Angelino Alfano, the ship began taking on water during the night after the motor was cut as it neared Conigli island off Lampedusa, a tiny speck of an island.

Usually smugglers have mobiles or satellite phones to call for help when they near shore or run into trouble, but this time they didn't. Instead, someone on board set fire to a piece of material to attract the attention of passing ships, only to have the fire spread to the ship itself.

The passengers all moved to one side to avoid the fire, flipping the ship and spilling hundreds of men, women and children into the sea, he said.