According to AP, David Heap, a spokesman for the Tahrir, identified those detained as Canadians Sandra Ruch and Soha Kneen, and Australian Michael Coleman. The boat tried to leave the southern Greek island of Crete on Monday, but was forced to turn back by Coast Guard vessels.

The Greek Merchant Marine Ministry said one of the Canadians, who was responsible for the boat, was arrested on charges of illegally sailing without permission. The other Canadian national and the Australian were arrested for using kayaks to block a coast guard vessel from setting sail to stop the flotilla boat.

Also Tuesday, a small group of activists from a Spanish-run boat in the flotilla entered the Spanish embassy in Athens and began a sit-in, hanging a Palestinian flag from a balcony and demanding that Spain pressure Greece to let their boat sail.

Manuel Tapial, a spokesman for the Spanish vessel Gernika, said the protesters were peaceful. A statement from the organization in charge of the vessel, Rumbo a Gaza, said protesters were not interfering with the work of embassy staff.

Greece last week banned all boats participating in Gaza Freedom Flotilla from leaving port, citing security concerns after a similar flotilla last year was attacked by Israeli forces, leaving nine Turkish activists on a Turkish boat dead.

Organizers of Gaza Freedom Flotilla said on Sunday they have not abandoned their plans to breach Israel's blockade of the territory despite a Greek government ban on their vessels leaving Greek ports.

The campaign suffered a major setback when Greece announced its restrictions on Friday, and authorities arrested the captain of a boat carrying American activists that tried to leave Greece without permission, AP reported.

However, organizers of the flotilla were trying to maintain momentum with planned protests in Athens in the face of increasing calls for them to scrap their campaign. On Saturday, the so-called Middle East Quartet of Mideast mediators -- the U.S., UN, EU and Russia -- urged governments to discourage Gaza-bound flotillas that could escalate tension in the region.

Activist Dimitris Plionis said there would be “some action” at the beginning of the week, but he did not specify what the pro-Palestinian activists were planning to do, presumably because Greek authorities might try to thwart their efforts.

“The ban is there and we have already said that we are still considering to sail,” Plionis said. “This story is not finished.”

Without elaborating, he noted that “ships are free to go to other locations” besides Gaza.

Photo: A Palestinian woman stands along the dock in the port at Gaza City on July 5, 2011, as international peace activists from Gaza Freedom Flotilla banned from setting sail for Gaza by Greek authorities occupied the Spanish Embassy in Athens. (Getty Images)