AT least 79 people have died and more than 100 have been rescued after their fishing vessel capsized off the coast of southern Greece.
But survivors and Greek officials say that hundreds more migrants were on board.
The government says this is one of Greece’s biggest migrant tragedies, and has declared three days of mourning.
The boat went down about 80 km (50 miles) south-west of Pylos after the coastguard said it had refused help.
The coastguard said the boat had been spotted in international waters late on Tuesday by an aircraft belonging to EU border agency Frontex. No-one on board was wearing life jackets, it added.
Quoting a timeline provided by the shipping ministry, Greek public broadcaster ERT said authorities had made contact with the boat via satellite phone on several occasions and offered help, but were repeatedly told: “We want nothing more than to go on to Italy.”
A few hours later, around 01:00 (23:00 GMT), someone on the boat reportedly notified the Greek coastguard that the vessel’s engine had malfunctioned.
Shortly after, the boat capsized, taking only ten to fifteen minutes to sink completely. A search and rescue operation was triggered but complicated by strong winds.
Alarm Phone, an emergency helpline for migrants in trouble at sea, said the coastguard was “aware of the ship being in distress for hours before any help was sent”, adding that authorities “had been informed by different sources” that the boat was in trouble.
It added that people may have been scared to encounter Greek authorities because they were aware of the country’s “horrible and systematic pushback practices”.
The boat is thought to have been going from Libya to Italy, with most of those on board believed to be men in their 20s.
They had been travelling for days, according to local media reports, which added that the boat had been approached by a Maltese cargo ship on Tuesday afternoon that supplied food and water.
Survivors spoke of as many as 500 to 700 people on board and regional health director Yiannis Karvelis warned of an unprecedented tragedy: “The number of the people on board was much higher than the capacity that should be allowed for this boat.”
Coastguard Cpt Nikolaos Alexiou told public TV that his colleagues had seen people packed on to the deck and that the boat had sunk in one of the deepest parts of the Mediterranean.