A British-flagged vessel has sunk of the coast of the island of Milos and a rescue operation is under way for 17 passengers at sea, the Greek coast guard says.
Four other boats, as well as navy and air force helicopters, are helping rescue efforts, and the circumstances surrounding the incident are as yet unknown.
The coast guard added it was not able to verify the nationalities of the passengers on board the board.
There is also no word on the type of ship that has sunk.