A boat carrying pro-Palestinian activists, who were attempting to break the blockade of Gaza has been seized by the Israeli navy who have forced it to sail to the southern port city of Ashdod, the army said.

The boat is said to include at least six activists from the UK.

The navy surrounded the vessel, which was said to be carrying humanitarian supplies to Gaza, and demanded the protesters turn back because of the security risks in breaking the blockade.

But the boat entered Gaza's coastal waters, and the navy boarded the boat to stop the protesters, though no shots were fired, an IDF spokesman said.

The crew will now be handed over to the Israeli authorities once ashore.

The IDF Spokespersons' Unit added that it "would like to emphasize that any organisation or country that wishes to transfer humanitarian aid to the Gaza Strip, can legally do so via the established crossings between Israel and the Gaza Strip with prior coordination."

The army said humanitarian goods found on board the boat would be transferred to the Gaza Strip, subject to authorisation.

The voyage's organisers, the Free Gaza Movement, said the vessel, renamed the Spirit of Humanity, left the Cypriot port of Larnaca on Monday bound for Gaza with three tons of medical supplies and children’s toys.

The 20 passengers are said to include former U.S. Representative Cynthia McKinney, Nobel Peace Prize laureate Mairead Corrigan Maguire and other activists from Britain, Ireland, Bahrain and Jamaica.

The Free Gaza Movement has organised five boat trips to Gaza since August
2008, all defying the blockade imposed by Israel put in place when Hamas
took control of Gaza in June 2007.

Two attempts were stopped by Israeli warships during Israel's offensive in December 2008 and January 2009.