Greek authorities have halted an international aid flotilla on its way to break the Israeli seige of Palestine.
Armed members of the coastguard have boarded the ship at various points over the past week. They have refused to give it permission to leave Greek waters.
One ship left the harbour without permission.
But it was caught by the Greek security forces and forced back to dock.
Another boat had its propeller damaged in what crew describe as an act of sabotage.
The capture of the flotilla comes as Greece moves to strengthen ties with the state of Israel.
On Monday, as activists were being harassed and ships held, Greek and Israeli military personnel were getting to know each other.
Their joint drill concluded a two-week programme held at Greece’s Larisa Air Base.