Reports from Turkey say that hundreds of passengers on board a Ukrainian cruise ship have sent out distress calls saying they are being held hostage by the crew.

The Anatolia news agency says passengers on board the ship, now anchored outside the Bosphorus straits, threw bottles containing messages into the water and held up signs saying they were in danger.

But the Turkish authorities say the ship's captain told them there were no problems and all is calm.

The ship the Taras Shevchenko, with more than five-hundred passengers on board, is on a three-week tour of the Mediterranean.