Dissension spread among the remaining passengers of the international Freedom Flotilla hoping to breach Israel's sea blockade on Gaza, after the US boat set sail unexpectedly Friday and was intercepted by the coastguard.
The Palestinian Islamist movement Hamas denounced Greece, describing the action as "inhumane" and saying Athens had played into Israeli hands, while activists slammed what they called an "out-sourcing of Israeli foreign policy."
The Ship to Gaza organisation said Greek Prime Minister George Papandreou had sold "Greece's soul," by allowing "Israeli territorial waters" to reach its shores.
Greece's Civil Protection Authority confirmed Saturday that the ban on departures of ships "with Greek and foreign flags from Greek ports to the maritime area of Gaza" was in place "until further notice."
With coastguards on the alert for copycat attempts to defy the ban from the other boats involved, the flotilla organisers argued over plans to get the remaining four boats into international waters and on to Gaza.
Activists have accused Israeli secret services of keeping the mission grounded through a campaign of harassement and dirty tricks, including "sabotage" attempts on two boats and a slew of bureaucratic problems.
Only four of the initial 10 boats were still in the running on Saturday: Spain's Gemika, the Canadian Tahrir and the French Dignity and Louise Michel. It is not clear whether they would carry the aid originally destined for Gaza.
The US Audacity of Hope had sailed without warning an hour after the Greek authorities announced their ban on Friday, and was quickly intercepted by a coastguard boat with six masked, armed men on board.
US Captain John Klusmer was arrested and ordered to appear in court Monday while the others were free to go but "chose to stay on the boat in solidarity with the captain and defiance of the Greek authorities," a spokesperson said. They were still on the boat on Saturday morning, which was being guarded at a small military port near Athens.
Furious "Boat to Gaza" organisers blamed Greece for complicity, claiming Israeli Prime Minister Benjamin Netanyahu had thanked Athens and world leaders for their stand against the "provocative flotilla".
Hamas immediately called on the EU parliament and human rights organisations "to put pressure on the Greek government" to allow the flotilla to set sail, but remaining activists began to fight among themselves over their next move.
Organisers had originally said they planned to wait for the "sabotaged" Swedish-owned Juliano to be fixed, but frustrated activists called for an immediate departure while others argued the futility of defying the Greek ban.
Would-be passengers of all ages had protested in front of the US Embassy in Athens on Friday, chanting "Gaza we are coming!" and "Free, free Palestine", as Greek police pushed them back with riot shields, but plans for a second day of protests were put on hold.