"I've been nervous, but today I'm excited,'' said Lauren Booth, 41, an activist and sister-in-law of Tony Blair, the former British prime minister.

"It's not about our fear, it's about the people waiting in Gaza, you can't think about
anything else.''

Palestinian confinement

Israel imposed the blockade after Hamas seized control of Gaza in June 2007, routing forces loyal to Mahmoud Abbas, the Palestinian president.

Gaza's 1.4 million Palestinians are already largely confined to their narrow strip of land by Israeli and Egyptian border closures.

A trickle of people are still allowed to leave for medical care, jobs abroad and for the
annual Muslim pilgrimage to Saudi Arabia.

Israel and Hamas have observed a fragile truce since June.

Israeli response

The boats departed after last-minute engine repairs to the Liberty, passenger safety drills and a final inspection of the vessels' hulls by Cyprus marine police divers.

"It's such a victory to leave the harbour without being sabotaged,'' said Adam Qvist, a 22-year-old Danish activist.

Group members sang a peace song in Arabic and formed the peace sign with their fingers before boarding the boats.

They plan to deliver 200 hearing aids to a Palestinian charity for children and hand out 5,000 balloons.

Lauren Booth, Tony Blair's sister-in-law, will join activists [AFP]

"Trying to breach the wall of silence surrounding Gaza is the best way to show that when a problem is hidden [it doesn't mean] it doesn't exist,'' said Tasos Kourakis, a Greek MP who joined the activists.

Israeli officials said the delivery is illegal because Gaza is controlled by Hamas, which it considers a terrorist group.

But they have refused to say how Israel would respond if the activists tried to break the blockade.

Paul Larudee, a Free Gaza organizer, said it's "highly unlikely" the Israeli navy would fire on the boats to stop them.

But he said the group expects Israeli authorities to intercept the boats and arrest those onboard.

Larudee said the group would contest any arrests in court on the premise that Israeli authorities committed kidnapping.