Human rights activists on board an Irish ship attempting to break the blockade on Gaza have been labelled hypocrites on a publicity stunt.
Former rugby player Trevor Hogan and several politicians are on the MV Saoirse, which is in international waters about 200 miles from Palestine.
The Canadian ship MV Tahrir also set sail as part of the Freedom Waves humanitarian mission. The vessels are carrying 27 passengers from seven countries who hope to reach Gaza on Friday.
Dr Fintan Lane, of the Irish Ship to Gaza group, said the only obstacle in their way was Israel's military - which last year killed nine Turkish activists taking part in the Freedom Flotilla to Gaza.
The MV Saoirse was also forced to pull out of a flotilla in June after it was damaged while docked in Turkey, which activists claimed was deliberate sabotage by Israel. "The Palestinians living in Gaza want solidarity - not charity," Dr Lane said. "Our primary goal is to help free Palestinians from their inhumane isolation in what is in effect an open-air prison."
But the Israeli Embassy in Dublin warned the vessels will be intercepted before reaching Gaza and accused those on board of being "hypocrites on a provocative publicity stunt".
"If these people care about human rights in the Arab world, why not take a flotilla to Syria, where over 3,000 people have been killed by the regime?" said a spokesman. "If they care about Palestinians, why not speak out against the Hamas regime in Gaza, which represses all dissent and the rights of women and homosexuals?"
Israel maintains it imposed the naval blockade to prevent weapons from reaching Hamas militants and that aid and consumer goods are reaching the area through Israel and Egypt.
Last year, nine people were killed when Israeli commandos stormed the MV Marmara, a Turkish aid ship trying to break the naval blockade. Each side blamed the other for the violence.
A UN panel report later blamed Israel, Turkey, and organisers of a Gaza-bound flotilla for the deadly raid. It found the blockade of Gaza was legal but it called the raid on the flotilla "excessive and unreasonable" and the killing of eight Turkish activists and a Turkish-American "unacceptable".