Greek authorities have arrested the captain of a boat that was due to carry activists to the Gaza Strip.
John Klusmire, a US citizen, is being held in custody at police headquarters in the port of Piraeus, near Athens.
The BBC reports he faces charges of trying to leave port without permission and of endangering the lives of passengers.
The boat, called the Audacity of Hope, is part of a flotilla planning to take humanitarian aid to Gaza to challenge the Israeli blockade of the Palestinian territory.
The Audacity of Hope, which is currently moored at a naval base, was carrying 36 passengers, four crew and about 10 members of the media.
Meanwhile Israel is denying claims it sabotaged two other ships that were to join this year's flotilla.
Last year nine activists on a Turkish aid ship were killed in a raid by Israeli commandos as it tried to reach Gaza.