Authorities have retrieved the bodies of 79 refugees after a fishing boat carrying an unknown number of passengers sank 47 nautical miles off Pylos town, Greek national news agency AMNA reported.
"Everyone’s thoughts are with all the victims of the ruthless traffickers who take advantage of human misery," said caretaker Prime Minister Ioannis Sarmas.
A total of 104 passengers have now been rescued, Nikolaos Alexiou, spokesperson for the maritime affairs and insular policy ministry told Greek national broadcaster ERT. A search and rescue operation to locate other passengers will continue during the night, he added.
"We cannot give a number of passengers with certainty, but it was very large ... My colleagues found an overloaded boat," he said.
However, he did not confirm estimates that there were 400-700 passengers on board, which survivors gave to ERT and other media. They said the fishing boat which sank during nighttime between Tuesday and Wednesday had been on the way from Libya to Italy.
The incident happened in the area with the deepest waters across the Mediterranean Sea, and none of the survivors was wearing a lifejacket, according to Alexiou.
Greek President Katerina Sakellaropoulou has travelled to the nearby city of Kalamata, where survivors are being taken. The president expressed deep sorrow over the tragedy, calling for "coordination of EU member states to safeguard the lives and safety of migrants and refugees."
Meanwhile, European Council President Charles Michel said the accident was a "heartbreaking reminder we must put an end to the unscrupulous business of smugglers." EU leaders will address the issue at the European Council on June 29-30, he said on Twitter.
"We must continue to work together, with Member States and 3rd countries, to prevent such tragedies," European Commission President Ursula von der Leyen said.
So far this year, 72,778 refugees have arrived in Europe from the south, including 71,136 arrivals by sea to Italy, Greece, Spain, Cyprus and Malta, according to the United Nations Refugee Agency UNHCR.
At least 1,037 people have died or been reported missing in the region since the start of 2023, according to UNHCR.