At least 130 African migrants have died and many more are missing after a boat carrying them to Europe sank off the southern Italian island of Lampedusa.
Ninety-four bodies have been recovered and a further 40 have been discovered inside the wreck, coast guards say.
Passengers reportedly threw themselves into the sea when a fire broke out on board. More than 150 of the migrants have been rescued.
Most of those on board were from Eritrea and Somalia, said the UN.
The boat was believed to have been carrying up to 500 people at the time and some 200 of them are unaccounted for.
Italian Interior Minister Angelino Alfano said the ship had come from Misrata in Libya and began taking on water when its motor stopped working.
This marked a tragic end to a long journey from countries as far as Eritrea and Somalia.
Over the years there have been numerous disasters involving migrants off Lampedusa, but seldom on anything like this scale. The island’s mayor wept as she took in the scene on the harbour wall.
Furious demands are being made for an end to the dangerous trafficking of people across the Mediterranean. But it is hard to see how the flow could be curbed, with so many people so desperate for a chance to make a new life in Europe, and traffickers in so many ports ready to take their money.
It is thought that some of those on board set fire to a piece of material to try to attract the attention of passing ships, only to have the fire spread to the rest of the boat.
Simona Moscarelli, a spokeswoman from the International Organization for Migration in Rome, told the BBC that in order to escape the fire, “the migrants moved, all of them, to one side of the boat which capsized”.
She estimated that only three of about 100 women on board survived, adding that most of the migrants were unable to swim.
“Only the strongest survived,” she said.
It is one of the worst such disasters to occur off the Italian coast in recent years; Prime Minister Enrico Letta tweeted that it was “an immense tragedy”.
Lampedusa mayor Giusy Nicolini: “These bodies are all speaking. We need to stop this”
“There is no miraculous solution to the migrant exodus issue,” said Italian Foreign Minister Emma Bonino. “If there were we would have found it and put it into action.”
In a separate incident on Thursday, local media reported that around 200 migrants were escorted to the port of Syracuse on the island of Sicily, when their vessel encountered difficulties five miles off the coast.
Footage from Lampedusa showed bodies being laid out on the dockside.
The mayor, Giusi Nicolini, described the scene as a “continuous horror”.
“It’s horrific, like a cemetery, they are still bringing them out,” she said, according to Reuters.
Rescued migrants arrive onboard a coastguard vessel at the harbour of Lampedusa
More than 140 people have been rescued from the shipwreck, officials say
This picture grabbed on a video released by the Guardia Costiera on October 3, 2013 shows some of the immigrants after their rescue near Lampedusa
The vessel reportedly capsized after a fire on board
Survivors of a ship carrying migrants which caught fire and sank off the Sicilian island of Lampedusa are seen aboard an Italian Coast Guard vessel
There are believed to have been around 500 people on board the vessel
Body bags containing African migrants, who drowned trying to reach Italian shores, lie in the harbour of Lampedusa
The bodies of the victims were lined up at Lampedusa dockside
Mr Alfano said at least three children and two pregnant women are among the dead. Local media reported that a suspected people smuggler had been arrested.
Pope Francis sent a Twitter message calling for prayers for the “victims of the tragic shipwreck off Lampedusa”. In July he visited the island and condemned the “global indifference” to the plight of migrants trying to arrive there.
In a later audience at the Vatican, he said: “The word is disgrace: This is disgrace!”
Estimated 7,800 migrants and asylum-seekers arrived in Italy in first half of 2013
Estimated 600 arrived in Malta in same period
Some 6,700 left from Libya and other parts of North Africa. Others crossed from Greece and Turkey
Most come from Sub-Saharan Africa, particularly Somalia and Eritrea. Others come from Egypt, Pakistan and Syria
40 recorded deaths in first six months of 2013
Almost 500 reported dead or missing in whole of 2012
In a statement UN High Commissioner for Refugees Antonio Guterres commended the swift action taken by the Italian coast guard to save lives.
Mr Guterres also expressed “dismay at the rising global phenomenon of migrants and people fleeing conflict or persecution and perishing at sea”.
At this time of year, when the Mediterranean tends to be calmer, vessels carrying migrants from Africa and the Middle East land on Italy’s southern shores almost every day, the BBC’s Alan Johnston reports from Rome.
But often the vessels are overcrowded and are not seaworthy.
The UN said that in recent months most migrants attempting the crossing were fleeing the conflicts in Syria and the Horn of Africa, rather than coming from sub-Saharan Africa.
The UN High Commissioner for Refugees said that more than 1,500 people drowned or went missing while attempting to cross the Mediterranean to reach Europe in 2011, making it the “most deadly stretch of water for refugees and migrants”.
“A disgrace”: Pope on boat tragedy
The UN also said that almost 500 people were reported dead or missing at sea during 2012 in attempts to reach Europe.
The number of those arriving by sea to Italy this year until 30 September stood at 30,100, according to the UN.
The main nationalities of those arriving were Syrian (7,500), Eritrean (7,500) and Somali (3,000).
On Wednesday a draft report from human rights body the Council of Europe said that Italy was “ill-prepared for a new surge of mixed migration on its coasts”.
Italy’s system for receiving and processing migrants and asylum seekers was not fit for purpose, a council committee on immigration said.