Israeli troops on Saturday boarded a boat carrying pro-Palestinian MPs and activists seeking to run its naval blockade on the Gaza Strip, blocking the latest attempt to reach the enclave by sea, the military said.

The operation, which the military said was concluded peacefully, ended the latest bid by activists to breach Israel's tight maritime embargo on Gaza which prohibits all naval traffic in and out of the Palestinian coastal territory.

"A short while ago, Israeli navy soldiers boarded (the MV) Estelle, a vessel which was en route to the Gaza Strip, attempting to break the maritime security blockade," the military said in a statement, indicating the Finnish-flagged vessel was being led to Ashdod port in southern Israel.

"There was no violence," a military spokeswoman told AFP, saying troops had taken control of the 53-metre (174-foot) vessel. "The passengers did not resist."

On board the ship are 17 passengers, among them five parliamentarians from Europe and a former Canadian lawmaker, organisers said. It was also carrying a shipment of humanitarian aid and 30 doves, which the passengers had been intending to release on arrival in Gaza.

The announcement came shortly after organisers told AFP that the ship had "come under attack" after being approached by navy vessels some 38 nautical miles off the Gaza coast.

The military said the boarding was carried out only after "numerous calls to the passengers onboard" which went unanswered.

"As a result of their unwillingness to cooperate and after ignoring calls to change course, the decision was made to board the vessel and lead it to the port of Ashdod," the military said, indicating that troops "did not need to use force."

On arrival at Ashdod, the ship's passengers would be handed into police custody and then onto the immigration authorities for immediate deportation.

The takeover of the MV Estelle was quickly denounced as "piracy" by Gaza's Hamas rulers.

"The occupation's attack on the Estelle and its capture of the activists on board is an act of piracy and a crime against humanity," said spokesman Sami Abu Zuhri.

"It should provide an extra incentive for ships showing solidarity with Gaza and for regional and international efforts to lift the siege on Gaza and end the suffering of its people," he said.

The move was also denounced by Gisha, an Israeli NGO which campaigns for Palestinian freedom of movement and trade.

"The question is not what is entering Gaza but rather what -- and who -- is being permitted to leave. Israel continues to prevent people in Gaza from travelling to the West Bank and marketing their goods outside Gaza, stifling economic and social development," the NGO said.

"If Israel wants to exercise its authority, as occupying power, to stop ships from reaching Gaza, it must fulfil its obligation to allow free movement of people and goods via the land crossings, subject only to individual security checks."

Ahead of the ship's arrival in Ashdod, a group of around 20 Israeli peace activists gathered on a nearby beach, holding up signs in English and Hebrew reading: "End the siege of Gaza" and "Blockade = war crime," an AFP correspondent said.

"We oppose Israeli policy, which seeks to maintain its control through siege and closure, strangulating the Palestinian people," said a coalition of Israeli rights groups, including the Coalition of Women for Peace, Yesh Gvul and the Public Committee Against Torture in Israel.

Earlier, organisers told AFP the ship had been attacked by Israeli vessels at around 1030 GMT.

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

Among those on board are parliamentarians Ricardo Sixto Iglesias from Spain, Sven Britton from Sweden, Aksel Hagen of Norway, and Vangelis Diamandopoulos and Dimitris Kodelas, both from Greece. Former Canadian lawmaker Jim Manly is also on board.

Activists organised a major attempt to break the Israeli blockade in May 2010, when six ships led by the Turkish-owned Mavi Marmara tried to reach Gaza.

Israeli troops stormed the Marmara, killing nine Turkish activists and sparking a diplomatic crisis with Ankara, which expelled the Israeli ambassador and has cut military ties with the Jewish state.

Since then, there have been several other attempts to reach Gaza by boat, all of which have been stopped by the Israeli navy, although there has been no repeat of the bloodshed.

Israel says its blockade is necessary to prevent weapons from entering the coastal territory, which is run by the Islamist Hamas movement.

Last year, a UN report on the flotilla raid accused the Jewish state of acting with "excessive force" but found that its naval blockade on the coastal territory was legal.