Athens, Greece (CNN) -- A U.S. ship whose passengers and crew had hoped to participate in a Gaza-bound flotilla was stopped Friday by Greek authorities shortly after getting under way and escorted back to port.
A Greek Coast Guard patrol vessel intercepted the "The Audacity of Hope" -- a U.S. vessel carrying 36 American passengers and four crew members -- roughly 10 minutes after it had left Perama, said CNN reporter Phil Black, who was aboard the boat and witnessed the incident.
Over the next few hours, the Coast Guard captain tried to persuade those aboard the "The Audacity of Hope" that the vessel was not seaworthy and that its papers were not in order.
As officials aboard the boat accused the Greeks of acting outside the law by keeping them from sailing, activists sang, chanted and waved signs in support of their mission.
But their attempt to sail to Gaza came to an end when an inflatable boat carrying an armed Greek military commando team told the activists to follow them back to port or face being boarded.
The Greek government said Friday that it will allow none of the nine other boats in the flotilla to sail to Gaza because their mission is too dangerous. The flotilla members accuse the Greek government of buckling to pressure from the Israeli government.
For their part, the Israelis have said they are mounting a diplomatic offensive to try to stop the flotilla from setting sail at all.
Dimitris Delavekouras, a spokesman for the Greek Foreign Ministry, confirmed that the vessel had been detained. Athens has warned that all ships bound for Gaza will be prohibited from leaving its ports.
The flotilla, which has faced a series of bureaucratic and technical delays, was organized to commemorate the first anniversary of a similar flotilla that resulted in a clash in international waters with Israeli navy commandos that killed nine people, including an American.
The flotilla is intended to challenge Israel's maritime blockade of the Gaza strip.
The decision to stop "The Audacity of Hope" is the "latest example of another government being strong-armed by Israel into colluding in its illegal blockade of the Gaza Strip," said Jane Hirschmann, an American who is one of the flotilla organizers.
"When governments fail to act, as they have done for so long when it comes to the human rights and freedom of the Palestinians, people of conscience must act in their stead," she said.
Flotilla organizers have called Gaza an "open-air prison" that is "under siege."
Israeli defense officials released a statement asserting that "it is clear that the goal of the flotilla organizers is provocation: to challenge Israel's right of self-defense against a terrorist group that has caused close to a million Israeli civilians to live under the constant threat of attack for the better part of a decade."
On Thursday, organizers said another flotillavessel -- the Irish ship Saoirse -- was sabotaged while anchored in Turkey's territorial waters.
The propeller of the Saoirse was damaged by what coordinator Fintan Lane said were explosives. "We believe that plastic explosives were used to blow and weaken the propel shaft, and this would have sunk the ship in open sea," said Lane.
Lane said the damage was similar to damage to another flotilla boat docked in Piraeus, outside of Athens.
He called on the Greek and Turkish authorities to investigate what he called an act of terrorism.
CNN could not independently verify the claim.
While Lane on Thursday did not outright blame Israel for the alleged sabotage, flotilla organizers have unleashed a number of accusations about the Israeli government's effort to block the planned voyage.
A spokesman for Israel's foreign minister said he was "not going to get inside accusations. They are vague. There is nothing behind them."
"We have not concealed our case, our arguments, our diplomatic efforts. It's all out in the open."
On Tuesday, the Israeli government said flotilla participants had threatened to kill Israeli military personnel should their boats be boarded. They alleged that the participants were stockpiling sacks of sulfuric acid on boats to be used in the event of any attacks on Israeli commandos.
Flotilla organizer Medea Benjamin dismissed the allegations as ludicrous, saying: "They see this nonviolent, rag-tag group of ships as such a threat they're using their entire propaganda apparatus, and their diplomatic and economic clout to try to stop 300 peace activists. It's pathetic."
In May 2010, the Mavi Marmara -- owned by the Turkish Humanitarian Relief Foundation, or IHH -- and five other ships were on their way to Gaza laden with humanitarian aid and about 700 activists from various countries when the Israeli soldiers boarded it.
In clashes with Israeli navy commandos, the nine people were killed.
An independent Israeli commission, led by retired judge Yaakov Turkel, found that the Israeli commandos "acted professionally and in a measured manner in the face of unanticipated violence" when they seized the Gaza-bound aid ship.
Secretary of State Hillary Clinton told reporters last Friday that she didn't think this year's flotilla plan "is useful or productive or helpful to the people of Gaza."
"We have certainly encouraged that American citizens not participate in the flotilla," she said, "and we are urging that all precautions be taken to avoid any kind of confrontation."
Clinton's comments followed a harsher statement by State Department spokeswoman Victoria Nuland, who criticized the organizers for "irresponsible and provocative actions that risk the safety of their passengers."
CNN's Kevin Flower, David McKenzie, Mitra Mobasherat and Alan Silverleib contributed to this report