Rescue boats fanned out on Thursday, searching for hundreds of refugees and migrants who feared dead after their overcrowded fishing boat capsized and sank while trying to reach Europe.
At least 79 people were confirmed killed in the disaster.
Rescuers pulled 104 passengers from a boat that sank in deep water off the coast of Greece early Wednesday as it attempted to travel from Libya to Italy.
Authorities fear hundreds of people – including women and children – may be trapped below deck.
If confirmed, it would make the tragedy one of the worst ever recorded in the central Mediterranean.
“The opportunity found [more survivors] Very little,” retired Greek coast guard admiral Nikos Spanos told state-run ERT television.
The International Organization for Migration estimates, based on interviews with survivors, that the boat was carrying 700 to 750 people, including at least 40 children. Save the Children puts that number even higher, around 100 children.
Reports said the ship sank about 80 kilometers (50 miles) from the southern coastal town of Pylos.
Refugee activists, refugee-rescue NGOs, some European politicians and Pope Francis have all expressed grief and outrage over the devastation.
The Vatican said the pope was “deeply devastated” and “praying for the many dead migrants, their loved ones and all those who have been traumatized by this tragedy”.
‘Should be a wake-up call for EU governments’
Aerial photos released by the Greek coastguard showed dozens of people on the upper and lower decks of the ship looking up, some with their arms outstretched, in the hours before it sank.
Alarm Phone, which operates a trans-European network supporting rescue operations, said it was alerted late Tuesday to people on board a ship in distress in Greek waters.
It said it had notified Greek authorities and spoken to those on board seeking help, whose captain had fled in a small boat.
Government officials said the boat’s engines stopped and it began to turn side to side before it capsized and sank around 2 a.m. Wednesday.
Most of the survivors who have been transferred to the port city of Kalamata so far are men, authorities said.
Al Jazeera’s John Psaropoulos reported from Kalamata that doctors had treated several survivors, dozens of them with “near-drowning” symptoms.
“They developed a form of pneumonia that occurs when the lungs are partially flooded with water,” he said. “Some were sent back to the warehouse where other survivors had been.”
As Greece declared three days of mourning, the remains of the victims were moved to cemeteries near Athens for DNA testing. The Coast Guard said search operations will continue as needed.
“[European Union] Member states have gone to great lengths to close all routes to children and their families seeking safety in Europe. Often their only option is the dangerous journey by boat,” said Daniel Gorevan, senior advocacy adviser for Save the Children.
“The fact that people continue to die in the Mediterranean should be a wake-up call for EU governments,” he warned.
Government sources said there was little chance of salvaging the wreck from the Libyan port of Tobruk. The international waters where the incident took place are among the deepest in the Mediterranean.
Independent refugee activist Nawal Soufi said in a Facebook post that she was in contact with the migrants on the boat in the early hours of Tuesday and that she remained in touch with them until 11pm (20 GMT) :00).
“They keep asking me what they should do and I keep telling them that the Greeks help will come. On the last call, the guy I spoke to told me unequivocally: ‘I feel like this is going to be our last night alive. ,'” she wrote.
Greece is one of the main routes into the EU for refugees and migrants from the Middle East, Asia and Africa.
Until last month, Greece, under a conservative government, had taken a tougher stance on immigration, building walled camps and tightening border controls.
The country is currently run by a caretaker government, pending elections on June 25.
Libya, which has seen little stability or security since a NATO-backed uprising in 2011, is a major departure point for those seeking to reach Europe by sea, with people-smuggling networks largely run by military factions that control the coast.
The United Nations has recorded more than 20,000 deaths and disappearances in the central Mediterranean since 2014, making it the most dangerous migrant crossing in the world.