MONTREAL - A ship carrying Canadian protesters bound for Gaza was prevented from leaving a port in Greece Friday as the country announced it was banning vessels heading to the blockaded strip.

Organizers said Greek coast guards boarded the ship, known as the Tahrir, and attempted to arrest a Canadian passenger for refusing to surrender the boat's registration papers.

Ultimately no one on board was arrested but passengers were told the ship would not be allowed to leave for Gaza, organizer Ehab Lotayef said from Montreal.

Meanwhile, another vessel carrying American protesters that tried to leave from a different Greek port was escorted back to shore.

The ships are part of a flotilla of nine Greek and foreign-flagged vessels that have been planning to break Israel's sea blockade and deliver aid to the Palestinian territory.

Israel contends its sea blockade stops weapons from reaching Iran-backed Hamas militants who control Gaza, and has warned it would stop any attempt to circumvent its restrictions.

A flotilla to Gaza last year ended in bloodshed, when nine people were killed and 45 were injured after Israeli soldiers boarded a Turkish ship.

Canadian foreign affairs Minister John Baird has called this year's convoy "provocative," while the United States and Greece had previously urged activists not to proceed with the flotilla, saying it could lead to confrontation and noted that there were other means of aid delivery.

But Canadian organizers with this year's flotilla said they aren't breaking any laws and will continue attempts to sail to Gaza.

"It is the blockade of Gaza that is illegal under international law," organizer Dylan Penner, who is in Greece, said in a statement.

"We have a legal and moral obligation to challenge the blockade, given the failure of the international community to act."

Despite the difficulties Friday, organizers said the Canadian delegation remains in good spirits.

Demonstrations supporting the flotilla are being organized for Saturday outside Greek consulates in Montreal, Toronto, and Vancouver, as well as the embassy in Ottawa.

"The protests will be continued on the streets of many countries around the world," Lotayef said.

The setback on Friday followed a week of administrative delays that organizers attributed to Israeli pressure on Greece, which is mired in an economic crisis and has grown closer to Israel as it seeks more foreign investment.

On Thursday, an Irish ship said it had to abandon plans to set sail from the Turkish town of Gocek because of what it called Israeli sabotage.

Earlier this week, activists said the propeller of a Swedish ship in a Greek port was sabotaged. Israel has not commented on the reports.

Greece's Civil Protection Ministry said coast guard authorities were ordered to take "all appropriate measures" to implement the ban on vessels setting sail for Gaza.

It also said the "broader maritime area of the eastern Mediterranean will be continuously monitored by electronic means for tracking, where applicable, the movements of the ships allegedly participating" in the flotilla.