At least 94 people died and up to 250 were missing after a boat packed with African migrants caught fire and sank off the southern Italian island of Lampedusa on Thursday.
The disaster occurred when the boat's motor stopped working and the vessel began to take on water, Italian Interior Minister Angelino Alfano said. People on board burned a sheet to attract the attention of rescuers, starting a fire on board.
"Once the fire started, there was a concern about the boat sinking and everyone moved to one side, causing the boat to go down," he told a news conference. The 20-metre (66 ft) vessel sank no more than 1 km (half a mile) from shore.
Bodies fished from the water were laid out along the quayside as the death toll rose in what looked like one of the worst disasters to hit the perilous route for migrants seeking to reach Europe from Africa.
"It's horrific, like a cemetery, they are still bringing them out," Lampedusa Mayor Giusi Nicolini told reporters.
Alfano said three children and two pregnant women were among the victims.
The disaster happened four days after 13 migrants drowned off eastern Sicily, and Italian President Giorgio Napolitano said action was needed by the European Union to stem "a succession of massacres of innocent people".
A fishing boat raised the alarm at around 7:20 a.m. (0520 GMT) and began pulling people out of the water before coastguard vessels arrived on the scene. The coastguard said 151 people had been rescued.
"If they had been able to use a telephone, they could have been saved," he said.
The search for survivors and victims continued within a four nautical mile radius, in water around 30-45 metres deep. Rescuers planned to extend the radius later in the day, in case bodies had been pulled away by the tides, he said.
U.N. High Commissioner for Refugees Antonio Guterres praised the rescue effort, but said: "I am dismayed at the rising global phenomenon of migrants and people fleeing conflict or persecution and perishing at sea."
Migrants frequently land on Lampedusa, just 113 km (70 miles) from the coast of Tunisia, often picked up at sea in dangerously overcrowded boats by the Italian coastguard.
Pope Francis, who visited the island in July on his first papal trip outside Rome, said he felt "great pain" for the "many victims of the latest tragic shipwreck today off Lampedusa".
"The word that comes to mind is 'shame'," Francis said in unscripted remarks after a speech in the Vatican. "Let us unite our strengths so that such tragedies never happen again."
The stream of migrants is a humanitarian and political problem for the Italian government. About 15,000 reached Italy and Malta - 13,200 and 1,800 respectively - by sea last year, the UNHCR says. Thousands more have arrived this year.
Calling the deaths of migrants "an endless tragedy," Foreign Minister Emma Bonino said: "The rescue operation began immediately but it is getting more difficult because now the weather is getting colder, they don't know how to swim, they don't know where to go."
Migrants who arrive in Italy are allowed to apply for asylum. Many of them are ordered to leave the country but often slip away to become illegal immigrants in Italy or elsewhere in the European Union.
Italy has pressed the European Union for more help to fight the crisis which it says concerns the whole bloc.
"This is not an Italian drama, this is a European drama," Alfano said. "Lampedusa has to be considered the frontier of Europe, not the frontier of Italy."