Even before the tiny number of survivors reached the safety of Italian soil, the Mediterranean was the scene of fresh tragedies. A boat carrying more than 90 migrants sank close to the Greek island of Rhodes.
At least three people, including a small child, died when the boat ran aground off the rocks of the Aegean island on a crossing from the Turkish coast. Rescue workers dragged survivors from the sea, some of them clinging desperately to bits of debris from the boat after it broke up.
Fisherman Vincenzo Bonomo, who helped search for survivors of the boat which capsized near Lampedusa south of Sicily, said: "We thought we had seen it all and instead ... I saw kids' shoes, jackets, I saw life jackets, I saw a notebook and a backpack and that little boy face down in a huge oil slick that marked the grave of so many of those poor people. But I could not find even one survivor. Not one."
Those rescued have revealed that many of the victims were locked inside the hold when the vessel sank.
The boat had three levels -- the hold, a second level, and the upper deck. Only those on the upper level had any chance of surviving when the vessel capsized, apparently after migrants rushed to one side of the ship when they saw a passing Portuguese merchant ship they believed would rescue them.
The asylum seekers are believed to have included 200 women and dozens of children.
"A few hundred were forced into the hold, the lowest level. They were locked in and prevented from coming out," said Giovanni Salvi, a prosecutor in Catania, who is leading the criminal investigation.
Hundreds more were locked into the second level, while the remainder were on the upper deck, probably after paying more to the smugglers.
Italy and Malta, already hard-pressed by the latest sinking, were racing to the aid of two more migrant boats in difficulty off the Libyan coast, with a total of 400 people on board. "It looks like there will be more tragedies before the survivors of Sunday's disaster have even arrived in Sicily," Gemma Parkin, from Save the Children, said. "If this doesn't galvanise international action then we'd be extremely worried about people's compassion and humanity."
One of the survivors of the Catania disaster, a 32-year-old Bangladeshi, told Italian officials that as many as 950 people may have been on board, though the Italian Coast Guard believes it more likely the vessel was carrying 700 migrants.
"There were also 200 women and 50 children with us. Many were shut in the hold. They died like rats in a cage," the Bangladeshi man was reported as saying by La Sicilia. He also told La Repubblica: "The traffickers closed the portholes to stop them from coming out and they have finished at the bottom of the sea."
The man was flown to a hospital in Catania where he is being treated for an unspecified infectious disease.
The other 27 survivors were on their way last night to Catania from Malta, where an Italian Coast Guard ship had earlier docked with the bodies of 24 migrants who drowned in the disaster.
Rescuers said they had found the survivors desperately struggling to stay afloat, surrounded by dead bodies and yelling for help.
"They were at the very limit of their strength. They shouted with their last reserves because they heard the sound of our engines. They wouldn't have lasted much longer," a coast guard official told Ansa, Italy's news agency.
Matteo Renzi, Italy's prime minister, compared the plight of the tens of thousands of people trying to cross the Mediterranean with the condition of slaves transported across the Atlantic from the Americas.
"When we say we are in the presence of slavery we are not using the word just for effect," he said. "Three or four centuries ago, unscrupulous men traded in human lives ... exactly the same thing is happening now."
Migrants and refugees who have survived the journey to Italy have described horrific conditions on board leaky boats and barely seaworthy dinghies with no food or water, no lavatories and a "class system" in which more affluent refugees from countries such as Syria secure a place on the deck while poorer Africans are forced into the hold.
"There were 400 people on the boat. I was downstairs, there were no windows down there," Ali, a teenage Somali boy who made it to the Italian island of Lampedusa in February, told officials from Save the Children.
"They didn't give us water otherwise we would have to go to the toilet. There is no toilet on the boat. If you were sick or went up to get air, the traffickers would shoot you. I was scared of drowning, I cannot swim."
Prosecutors in Catania have opened an investigation into the tragedy, with a view to identifying and extraditing the smugglers in Libya. But with Libya torn between two rival governments, battling militias and a growing Isis (Islamic State) presence, the prospect of swift arrests seemed remote.
