ATHENS (AFP) - Defiant pro-Palestinian activists vowed Thursday to overcome alleged sabotage and a bureaucratic nightmare to bring aid to Gaza, in breach of Israel's sea blockade. "Let me assure you all: we will sail, whether we have official clearance to do so or not," coordinator Claude Leostic said in Athens, where a multi-national flotilla has been stuck for days. Israel's Foreign Minister Avigdor Lieberman called Thursday on the organisers of an aid flotilla for Palestinians in Gaza, now under an Israeli blockade, not to create "new friction" in the region. "I think there are enough problems in the Middle East. It's not necessary to create a new headache, new friction," Lieberman said after a meeting in Vienna with his Austrian counterpart. Demonstrations on behalf of the flotilla are planned for Friday in the capital, the scene of fierce riots this week by Greeks protesting against a fresh austerity package. Irish boat "Saoirse" suffered damage in a "sabotage" attack and pulled out of the mission, while a Spanish vessel joined the long list of boats told by Greek port authorities they had problems with their paperwork. Anger mounted among the hundreds of volunteers gathered from 22 countries after the Irish Ship to Gaza (ISG) campaign said Israel was "the chief suspect" in the incident, which followed an similar incident involving a Greek boat. "Mossad's behind this for sure," said one passenger who asked not to be named. "You don't think these attacks were done by amateurs do you? We have to be very careful about what we say and do, we're under surveillance."