Greek authorities have arrested the captain of one of the ships from the Freedom Flotilla II for illegally setting sail for the Gaza Strip, the Greek Coast Guard said on Saturday.
European human activists have been campaigning to end Israel's blockade of Gaza and attempting to send humanitarian aid to the enclave.
Israel cut off access to the Gaza Strip in the middle of 2006 after Palestinian Islamists abducted Israeli serviceman Gilad Shalit. Israel has since threatened to thwart any attempts to approach the enclave from sea and urged humanitarian vessels to unload their aid at other ports.
The ship's captain, aged 60, of the Audacity of Hope, one of at least 10 ships in the flotilla, ignored port authority orders and attempted to leave Greek territorial waters without permission and head for Gaza.
The Audacity of Hope, flying under a U.S. flag, had 36 passengers, 10 journalists and a crew of four on board.
The captain, whose name has not been released in line with Greek law, will be questioned on July 5. If found guilty of violating port authority orders, he could face up to two months behind bars.
Rami Abdo, a spokesman for the European campaign, said unidentified divers, presumed to be from Israel's Mossad intelligence service, broke the engine of an Irish ship on Thursday when it was anchored in a Turkish port in a bid to disrupt its departure.
Flotilla spokesman Dror Feiler said there was no direct evidence Israel was involved, The Jerusalem Post reported on Thursday, citing a statement provided to Israeli Army Radio.
The European anti-blockade campaign has called on European countries to defend the Freedom Flotilla II against any Israeli aggression. In May 2010, Israeli commandos seized control of a Turkish vessel, the Mavi Marmara, which was part of the first Freedom Flotilla. Nine activists died in the raid near the Gaza coast, with each side blaming the other for the fatalities.
