At least 104 were rescued, but the death toll is feared to rise, as survivors indicated that the boat was carrying up to 700 migrants, mostly from Pakistan, Egypt and Syria.

According to the source, some of the victims said that among the passengers were many women and children, while the Greek Coast Guard noted that it is difficult to determine exactly how many people were on board.

Greek authorities are investigating three survivors on suspicion of being human traffickers, who attracted attention with their relaxed attitude after being rescued and taken to the city of Kalamata.

All those rescued will be interviewed as part of a preliminary investigation to clarify the causes of the tragedy, ERT said.

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