But Greek officials and the International Organization for Migration (IOM) say that hundreds of people could have been on board

Greece's coastguard said the boat was spotted in international waters late on Tuesday by an aircraft belonging to EU border agency Frontex. The coastguard said that the passengers "refused any help" and that none on board were wearing life jackets

But just a few hours later, the boat capsized and sank, triggering a search and rescue operation, which was then complicated by strong winds.

The boat was reportedly en route to Italy from Libya, with most of those on board reportedly men in their 20s

A migration ministry source told the AFP news agency that "hundreds" of people were on board. "We fear there will be a very large number of missing persons," the official said.

The IOM tweeted: "We fear more lives were lost. Initial reports suggest up to 400 people were on board."

The nationalities of the victims have not yet been announced. Survivors have been taken to the town of Kalamata for treatment