The Greek coast guard took control Monday of a Canadian ship in a flotilla carrying activists who say they are bringing humanitarian aid to Gaza.
The Tahrir, bearing at least 30 Canadians, left a Greek port late Monday afternoon local time and was boarded 15 minutes later by armed Greek coast guard officers.
In a phone interview, activist Dylan Penner told CBC News that two Greek Coast Guard officers had boarded the ship.
Penner said one officer had a pistol drawn as he stepped over him to get to the Tahrir's wheelhouse and take control of the vessel.
Penner said that to his knowledge there had been no injuries. However, he called the ship seizure "illegal and a violation of our human rights."
It was unclear whether the ship would be impounded or if any of the activists faced arrest.
The Tahrir was one of several vessels aiming to breach Israel's Gaza Strip sea blockade in an attempt to deliver the activists' aid.
The Harper government has criticized the flotilla, but the Canadians on board the ship are calling on Ottawa to denounce what they view as an unlawful act by the Greek government.
Greece last week banned all boats participating in the Gaza flotilla from leaving port, citing security concerns after a similar flotilla last year was raided by Israeli forces, leaving nine activists on a Turkish boat dead.
The Greek foreign ministry has offered to deliver the humanitarian aid the activists want to take to Gaza itself.
Israel says it imposed the blockade in 2007 to stop weapons reaching Hamas, the Islamic militant group that rules Gaza. Israel eased its land blockade after an international uproar over last year's raid on the Turkish boat.