Two Canadians linked to a flotilla seeking to leave Greece for the Gaza Strip have reportedly been detained by authorities.
David Heap, a spokesman for a boat carrying dozens of Canadians, says an Australian was also arrested and that all three could face charges.
He identifies the Canadians as Sandra Ruch and Soha Kneen and the Australian as Michael Coleman.
Activists say the Greek coast guard had earlier damaged the Canadian ship by ramming it against a cement pier after forcing it back to shore.
The Tahrir, bearing at least 30 Canadians, left Greece on Monday evening local time and was boarded 15 minutes later by armed officers from the Greek coast guard.
Activists first believed the ship was sinking due to the hard landing. While it appeared the damaged ship would stay afloat, it remained confined to a Greek port late Monday after an unsuccessful attempt to reach Gaza.
Within an hour, the ship was back at another Greek port, where supporters of its mission were gathering.
"They arrived back to land into a location ... where the coast guard forced them to go to. Not the original dock," Ehab Lotayef, a Montreal-based spokesman for the ship, told The Canadian Press in a telephone interview.
"They slammed it into the concrete, into the pier-side."
Mr. Lotayef said several dozen activist passengers remained late Monday on board the ship, which was damaged and leaking diesel.
"We are holding the Greeks responsible for all that - totally unjustified action by the Greek government, arm-twisted by the Israelis," he said.
"It is a setback but it's not the end of the road. The efforts will continue worldwide until this blockade ends."
No one on board was believed to be injured, and no shots were fired, but the Greek coast guard blasted a water cannon at the ship as it left port, said activist Dylan Penner.
The Canadian activists called on Ottawa to denounce what they view as an unlawful act by the Greek government.
"This is a peaceful international mission to break Israel's illegal blockade of Gaza which, it is now crystal clear, has been extended to the ports of Greece," said Mr. Penner.
"I wouldn't say it's a surprise but it's certainly shameful. We have every right to bring the aid we are attempting to bring to Gaza to break the siege," he added.
The Tahrir was one of several vessels aiming to breach Israel's sea blockade of the Gaza Strip in an attempt to deliver the activists' aid.
-- with files from The Associated Press