A ship carrying pro-Palestinian activists seeking to breach Israel's naval blockade on Gaza has been seized shortly after being approached by Israeli vessels.

"The Estelle is now under attack - I have just had a message from them by phone," Victoria Strand, a Stockholm-based spokeswoman for the Ship to Gaza Sweden campaign told the AFP news agency on Saturday.

According to Dror Feiler, another spokesperson, the SV Estelle, whose passengers included five parliamentarians from Europe and a former Canadian politician, was boarded at around 08:15 GMT.

"Five or six military vessels surrounded the Estelle. Soldiers wearing masks are now trying to board the ship. The attack took place on international water: N31 26 E33 45," Feiler said. The Israeli military confirmed that the ship was boarded.

"A short while ago, Israeli navy soldiers boarded Estelle, a vessel which was en route to the Gaza Strip, attempting to break the maritime security blockade," it said in a statement.

The military also said no one was hurt when marines boarded the vessel, a three-mast schooner, and that it was rerouted to the Israeli port of Ashdod after it ignored orders to turn away from the Hamas-governed Palestinian enclave.

The Estelle, the latest ship to try to break Israel's blockade on Gaza as part of the "Freedom Flotilla" movement, had set sail from Naples in southern Italy.

Luigi de Magistris, the mayor of Naples, met with members of the crew during a visit to the Estelle in the city's port.

The Estelle, whose voyage was organised by an international pro-Palestinian coalition, was carrying humanitarian goods such as cement and books to the Gaza Strip.

There were 30 activists from around the world on board, including passengers and crew from Canada, Israel, Norway, Sweden and the US.

(Agencies via Al Jazeera)