The 60-year-old captain, whose name was not released by authorities, was being held at Piraeus police headquarters and will remain there until a court hearing Tuesday.

Greece’s coast guard said the captain of "The Audacity of Hope" faces charges of trying to leave port without permission and of endangering the lives of the boat’s passengers. The latter charge is a felony.

The boat was carrying 36 passengers, four crew and about 10 members of the media. Its attempt to sail Friday night from the port of Perama, near Athens, was thwarted by coast guard speedboats. On the same day, Greece had announced it was banning vessels heading to Gaza from leaving Greek ports.

In Jerusalem, Israel has denied claims it sabotaged ships trying to breach its sea blockade of the Gaza Strip.

Activists have accused Israel of damaging two ships docked in Turkey and Greece that were part of a flotilla attempting to reach the Palestinian territory.

Israeli Foreign Ministry spokesman Yigal Palmor dismissed the sabotage charges as "ridiculous," calling them "sad conspiracy theories."

Selcuk Unal, a spokesman for the Turkish Foreign Ministry, said authorities had determined that there was no act of sabotage on an Irish vessel in the flotilla that docked in the Turkish port of Gocek on the Aegean Sea.

Israel says it imposed the blockade in 2007 to stop weapons reaching the Islamic militant group Hamas that rules Gaza. Activists describe the blockade as a form of incarceration for the Palestinians.

Nine activists on a Turkish boat were killed last year in an Israeli raid on a similar flotilla.

In a statement, the Middle East Quartet of Mideast mediators — the U.S., U.N., EU and Russia — said it remained concerned about the difficult conditions facing Palestinians in Gaza, but noted "a marked increase in the range and scope of goods and materials" entering Gaza over the last year.

It urged those wishing to deliver goods to Gaza to do so through "established channels," which include Israeli and Egyptian crossings.

The Quartet "urges restraint and calls on all Governments concerned to use their influence to discourage additional flotillas, which risk the safety of their participants and carry the potential for escalation," the statement said.

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Ian Deitch in Jerusalem and Selcan Hacaoglu in Ankara, Turkey, contributed to this report.