|The boat left the Greek port of Perama [Reuters]
A boat carrying dozens of US activists seeking to break Israel's blockade of the Gaza Strip has been towed back to port by a Greek coast guard after setting sail from a port in Greece.
The boat, dubbed The Audacity of Hope, is one of nine vessels carrying several hundred activists who say they want to deliver aid to the Palestinian territory. The boat left the port of Perama on Friday.
Joseph Dana, a journalist for the Nation magazine on board the boat, told Al Jazeera that the ship left the port of Perama and sailed for an hour after which it was intercepted by a Greek coast guard ship that demanded it return to the port.
"We were surrounded by commandos pointing live weapons at the ship," he said.
"Now we are following one major coast guard vessel and we are [being] tracked by two other zodiac vessels.
"The commandos are still on board, but they are not pointing weapons anymore."
The boat is returning back to a port, but the ship is returning to a different port for fear of sabotage attempts, Dana said.
The boat has not been free of sabotage attempts. On June 24, an annonymous complaint was filed against the ship's "seaworthiness". The Israel Law Centre (Shurat HaDin), took responsibility for the complaint in the Israeli press.
The Greek embassy in Tel Aviv put out a statement confirming that the Greek coast guard has enforced a decision by the Civil Defence to prevent all flotilla vessels from leaving Greek ports.
Greece's Civil Protection Ministry said coast guard authorities had been ordered to take "all appropriate measures'' to implement the ban.
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.
"What I am witnessing right now at this moment is Israeli diplomatic pressure on the Greek government to ensure that these boats do not leave any port inside Greece," Dana said.
Meanwhile, activists from the Dutch-Italian ship on the Greek island of Corfu were also briefed by the flotilla organisers on Greece's decision to ban all boats from leaving.
Khaled Tuhraani, one of the leaders on the Italian-Dutch ship Stefano Chiarim, said that the activist should come up with "Plan B".
"Every group on board should consult each other about what they want to do next. We'll have another meeting tonight at ten o'clock to discuss all our options," Tuhraani said.
Some of the activists were clearly disappointed and angry, and suggested staging a protest against the Greek government in Athens.
Feeds from Twitter, the microblogging site, said that the Canadian boat dubbed Tahrir has been blocked from leaving by Greek authorities.
Israel has said it will thwart any effort to breach the blockade.
Binyamin Netanyahu, Israel's prime minister, said in a speech to graduating army cadets on Thursday: "I would like to praise the many leaders throughout the world who worked against the 'provocation flotilla,' led by US and European leaders, [the] UN secretary general and my friend the Greek prime minister."
Mark Regev, a spokesperson for Netanyahu, asked about activists' allegations that Israel was behind the apparent sabotage attempts, was quoted in the New York Times on Friday saying: "These activists are not renowned for being an objective source of information.
"These people have a tendency to blame Israel, to see Israel's hand behind every calamity."
An Israeli raid on a similar flotilla last year left nine activists on a Turkish ship dead.
On Thursday, activists on board an Irish ship, the MV Saoirse, at the Turkish coastal town of Gocek, said it had to abandon plans to set sail because of what it called Israeli "sabotage".
Earlier this week, activists said Israeli agents damaged the propeller of a Swedish ship in the Greek port of Piraeus.