At least one assailant claiming to have a bomb hijacked a passenger ferry carrying 21 people in northwest Turkey on Friday, local officials said. Coastguard vessels were tracking the ferry east of Istanbul, they said.
Kocaeli Governor Ercan Topaca said there were 17 passengers and four crew on the Kartepe ferry which was travelling between Izmit and Golcuk in the Gulf of Izmit when it was hijacked around 5.45pm (1545 GMT).
Some reports said there was only one hijacker but others said there were four or five assailants who had overpowered the captain of the ferry and seized passengers' mobile phones.
It was unclear who was behind the hijacking but broadcaster NTV reported a claim that an assailant said he was a member of the Kurdistan Workers Party (PKK) militant group.
Three coastguards and a helicopter were following the 400-passenger capacity ferry, CNN Turk reported.
Kurdish, leftist and Islamic militants are all active in Turkey, but hijackings are rare. More than 40,000 people have been killed in the PKK insurgency since the group took up arms against the state in 1984.