Two converted fishing boats set sail from Cyprus on Friday carrying 44 activists determined to break the Israeli blockade of the poverty-stricken Gaza Strip.

The boats left from Larnaca port on the island's south coast at 9.50 am (0650 GMT) to cheers from a small crowd of supporters and despite death threats to activists on board.

They were being escorted by a coast guard boat, which officials said would stay with them until they were three nautical miles from the Cyprus coastline.

Those on board hail from 14 countries and are aged between 22 and 81, organisers said. Among them are students, lawyers, journalists and an online poker player.

Although organisers for the US-based Free Gaza Movement fear the Israelis might sabotage the 370 kilometre (230 mile) sea voyage to Gaza, they are confident of reaching their destination.

Many of those making the trip said they had received death threats.

The group hopes that the vessels will draw attention to the plight of Gaza's 1.5 million residents. Israel has sealed off the territory to all but very limited humanitarian supplies since the Islamist Hamas group seized control in June 2007.

The activists, mostly American and British, include Lauren Booth, sister-in-law of former British premier Tony Blair who is now an international Middle East peace envoy.

The two boats -- Liberty and Free Gaza -- are sailing under Greek flags and are carrying 200 hearing aids for Gaza children and 5,000 balloons.

"The goal of our voyage is to break the illegal siege on the people of Gaza as a step toward ending the Israeli occupation of Palestine," the Free Gaza Movement said in a statement released as the boats set off.

"To remove any 'security' pretence that Israel may raise, we have had our boats inspected and certified by Cypriot authorities that they carry no arms or contraband of any kind," it added.

"We are human rights activists, invited to visit Gaza by our Palestinian partners ... If Israel chooses to forcibly stop and search our ships, we will not forcibly resist. Such a search will be under duress and with our formal protest. After such a search, we fully expect the Israeli navy to stand aside, as we continue peacefully to Gaza."