LARNACA, Cyprus - Activists said Wednesday they were determined to break the Israeli blockade of the poverty-stricken Gaza Strip by boat despite receiving death threats.

"I've been called personally 17 times and asked how and when I would like to die," Palestinian activist Osama Qashoo told AFP.

"They also called my family in the West Bank and threatened to kill them, so there's lots of pressure, it's moral and psychological terrorism."

Qashoo said he traced one phone number to an Israeli network but couldn't say who was behind the intimidating threats.

Two converted fishing boats carrying 40-odd activists are due to set sail from Cyprus on Thursday for the 370 kilometre (230 mile) sea voyage to Gaza in a bid to break the blockade.

The boats, which arrived in Cyprus on Tuesday, are currently docked at Larnaca port on the island's south coast where Cypriots officials are checking everything is in order.

Although organisers for the US-based Free Gaza Movement fear the Israelis might sabotage the trip, they are confident of reaching their destination.

"We will try leave tomorrow night if everything falls into place, that's the intention," organiser Paul Larudee told AFP.

"People have threatened to blow the boats up, we are worried, but that's not going to stop anybody. I think we will succeed."

In 1988, a ferry planning to return Palestinian deportees to the Israeli port of Haifa was the target of a limpet mine attack off Cyprus's second city of Limassol a day after three Palestinian organisers were killed by a car bomb.

Israel's Mossad secret service was blamed but the Israelis denied involvement.

According to the Free Gaza Movement, the Israeli government contacted the Cyprus authorities to see if the boats could be stopped but was told "no."

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 84-year-old Holocaust survivor Hedy Epstein and 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 -- will sail under Greek flags and carry 200 hearing aids for Gaza children and 5,000 balloons.

"What can the Israelis do to two little boats?" asked 57-year-old Jeff Halper, the only Israeli Jew on the mission. "When might meets justice, justice always wins."