The Greek government issued a statement on Friday, saying that the departure of ships with Greek and foreign flags from Greek ports to the maritime area of Gaza has been prohibited. The statement explained that this is in a bid to prevent a breach of Israel’s naval blockade.

The Greek government stressed that local Hellenic Coast Guard Authorities must take all appropriate measures to implement the decision. It also warned that the broader maritime area of the eastern Mediterranean Sea will be continuously monitored by electronic means for tracking the movement of ships trying to participate in the flotilla.

Naval authorities have already implemented the order, blocking both an American and Canadian ship planning to participate in the pro-Palestinian Gaza flotilla set to take place next week.

However, in light of Greece's decision to block all ships heading to the strip, the flotilla has been delayed further.

American activists attempted to set sail from Greece toward Gaza on Friday aboard a boat dubbed "The Audacity of Hope", defying calls from Israel to cancel and the ban by Athens.

The boat left Perama port for the open seas, a Reuters witness said.

Shortly after leaving the port, Greek authorities stopped the boat, and the boat was sent back to a Greek naval port several hours later.

The “Tahrir”, a Canadian boat also planning to participate in the flotilla, remained docked on Friday after port authority officials boarded the ship demanding its license. Activists handed over the documentation; however they claimed that the ship fulfills all the necessary criteria needed to set sail.

Sandra Ruch, owner of the Tahrir, is currently meeting with port authorities in a bid to get the ship’s license back.

David Hick, head of the steering committee for the flotilla and a linguistics professor from Canada told Haaretz that port authorities gave no grounds for taking away the Tahrir’s license, only saying that this was a directive from the Greek president’s office not to allow ships to embark from Greek ports.

The Audacity of Hope and the Tahrir are two of the boats planning to take part in a flotilla aimed at challenging Israel's naval blockade of the Gaza Strip. A spokeswoman announced Friday that it will set sail next week, in spite of repeated delays that activists blame on Israeli sabotage.

"Israel is doing its very, very best to make sure we don't get out of port," spokeswoman Greta Berlin said, speaking by telephone from Greece where some of the ships are moored.

"We want to move the boats by July 5 to get to our rendezvous point no later than July 6 or 7 ... We will go with what we have," she added.

The original plan was to have 15 ships set sail, however the current count stands at nine boats hoping to take part in the mission, Berlin said in her statement.

The flotilla is set to head toward Gaza a little over a year after Israeli marines stormed another pro-Palestinian flotilla that had approached the strip. Nine activists died in the on-board clashes, provoking an international outcry.