"The only weapons I ever carried were while I was a US marine serving in the Gulf War," he said speaking from Turkey following his deportation from Israel.
"If they had a supposed terrorist in their possession, why the hell did they let me go?" O'Keefe said.
Fatima Mohammadi, another activist on board the Mavi Marmara that Israeli soldiers stormed last Monday in an attempt to stop a flotilla of aid ships from reaching Gaza, was accused of attempting to smuggle banned electronic componants into Gaza.
She told Al Jazeera through a spokesperson that she refused to dignify the accusation with a response.
The allegations come as part of an Israeli PR offensive seeking to counter a wave of condemnation over the raid, which left nine pro-Palestinian activists dead and dozens wounded.
'Lack of evidence'
Israel has continued to reject calls for an international inquiry into the attack, instead insisting that it should investigate the events surrounding the deaths of the activists itself.
Binyamin Netanyahu, the Israeli prime minister, said earlier on Sunday that "dozens of thugs" from what he called "an extremist, terrorism-supporting" organisation had boarded the flotilla and readied themselves for the arrival of the naval commandos.
"This group boarded separately in a different city, organised separately, equipped itself separately and went on deck under different procedures," he said.
"The clear intent of this hostile group was to initiate a violent clash with (Israeli) soldiers," he said.
|Netanyahu said extremist "thugs" were on board the convoy [AFP]
Ayman Mohyeldin, Al Jazeera's correspondent reporting from Jerusalem, however, said all cargo and passengers on board last week's convoy were required to pass through customs and port security whether they boarded in Greece, Ireland or Turkey.
"Israel has yet to provide evidence that any attack on its soldiers was in fact pre-planned - something denied by all those travelling on board the ship," he said.
Jamal el-Shayyal, Al Jazeera's correspondent who was on board the Mavi Marmara from the beginning of its voyage, said no such group joined the ship after it had left port.
"Not less than 24 hours before Israel attacked I was granted access to all areas of the ship to see whether there were any unwanted people or weapons on board," he said.
"There was nothing of this sort on the boat… The only way for someone to get on board without being screened would be if an aircraft dropped them on board, and the only one that did this was an Israeli military one, and it ended up killing people."
In an exclusive interview with Al Jazeera, Mahmut Tural, the captain of the Mavi Marmara, said none of the passengers on the boat took violent action against Israeli soldiers until they were attacked first.
"Only after the soldiers starting attacking the passengers, did they take away the soldiers' guns. The passengers on the boat in no way attacked the soldiers. They defended themselves. And that's natural," he said.
Farouq Burney, who represented Qatar on board the Mavi Marmara, also cast doubt on Netanyahu's claims.
"Most of the people who boarded the ship in international waters were renowned figures, like European MPs, a former US ambassador and a few people from the Free Gaza Movement," he said, referring to one of the flotilla's principal organisers.
"There is no way these people could be branded as terrorists."
Meanwhile, France's foreign minister said on Sunday that the European Union is willing to check cargo on board ships heading to the Gaza Strip if Israel ends its blockade of the territory.
"We can check the cargo of ships heading toward Gaza- we can do it, we
want to do it, we would gladly do it,'' Bernard Kouchner said, after a meeting with British foreign minister William Hague.
He said that the EU has had monitors deployed at Gaza's Rafah crossing with Egypt in the past and could do so again. France and Britain have both called for an immediate end to the blockade of Gaza and an international investigation into the raid on the Mavi Mamara.
Joseph Biden, the US vice president, said after a meeting with Egyptian president Hosni Mubarak that the US would seek "new ways to address the humanitarian, economic, security, and political aspects of the situation in Gaza."