An Irish American former marine has threatened legal action against the Israeli Government after they beat him on board the Gaza flotilla and publicly branded him a terrorist.

Californian Ken O'Keefe, 41, who travels on an Irish passport, took part in the recent Gaza aid flotilla.

The Israeli Defence Forces (IDF) says O'Keefe was a “radical anti-Israel activist and operative of the Hamas terror organisation”.

The IDF also claimed that O'Keefe had previously attempted to enter Gaza "in order to form and train a commando unit" for Hamas.

Nine of the activists on board O'Keefe's boat were shot dead by Israeli commandos while the IDF said that five passengers on the Turkish boat Mavi Marmara were "known to be involved in terrorist activity."

O'Keefe currently resides in London and took out an Irish passport in 2003 thought his Kerry grandmother.

O'Keefe has never taken British citizenship and renounced his US citizenship in 2001.

Speaking to the Irish Times newspaper from Turkey, O'Keefe said the Israelis had made a "massive mistake" by labelling him as a Hamas operative. O'Keefe now believes these allegations will put his life in jeopardy.

"There is no evidence to support this idea that I was going to train a commando unit in Gaza. Who the hell came up with that one?" said O'Keefe.

"Suing them is definitely an option. Not only is this slanderous, but if they are really serious, am I on a hit list now? Will a Mossad hit squad come and get me? They did that recently in Dubai, and look what they did with the flotilla last week.”

In 2004, O'Keefe was arrested for attempting to enter Gaza. He claims that he intended to meet with Hamas and Islamic Jihad officials in Gaza, in an effort to bring 10,000 international observers to Palestine.

“I told [the Israelis] during interrogation that I had met with people they deem terrorists. I spent 20 days in jail before they deported me as a security threat and barred me for 10 years,” he said.

O'Keefe admits that he met Hamas leader Ismail Haniyeh and other senior figures two years ago, when he took part in the Free Gaza Movements first attempt to break the Naval blockade.

However O'Keefe insists those meetings were to “make an introduction for the government of Hawaii (where Mr O’Keefe’s mother lives) and discuss a dialogue initiative”.

Asked whether or not he met other officials from Gaza militant groups he said, "I met so many people there that I couldn’t possibly know all their connections or backgrounds. I don’t ask for people’s CVs when I meet them.”

O'Keefe was subsequently deported to Turkey after he was illegally detained aboard the aid flotilla. O'Keefe is due to fly home to Ireland next week.

Ken O'Keefe: Irish American and member of the humanitarian aid flotilla