Israeli forces boarded a Gaza-bound ship Saturday, preventing the Irish-owned vessel from breaking through a naval blockade of the territory ruled by Hamas.

Israel naval vessels surrounded the MV Rachel Corrie — named after an American activist killed by an Israeli army bulldozer in 2003 — after trailing the ship for six hours. They sent four warnings, telling the crew to sail to the nearby Israeli port of Ashdod.

The 1,200-tonne vessel was carrying aid, along with 11 pro-Palestinian activists and eight crew members as it was intercepted in international waters, about 30 kilometres from Gaza's shore.

Israeli officials offered to unload the humanitarian aid and deliver it overland to Gaza, but the activists refused.

But Israeli forces avoided a repeat of Monday's events on the Turkish aid ship Mavi Marmara as it escorted the Irish ship to Ashdod.

Military spokeswoman Lt.-Col. Avital Leibovich said Saturday's takeover took just minutes as the ship's captain gathered passengers in one area of the vessel, presumably to avoid violence.

She said commandos clambered onto the boat by sea, instead of descending from helicopters as occurred Monday when commandos were attacked and nine activists were killed.

The military said the crew of the Rachel Corrie dropped down one of the ship's ladders to make it easier for the forces to board. The activists were sitting down when the troops boarded.

"We had six interceptions last week also but only one of them turned violent. It's the same Israeli navy using the same standing orders," said Mark Regev, a spokesman for the Israeli government. "It's clear that the violence last week came from the other side."

The 11 passengers and eight crew members will be deported, although those who object will be detained and given a chance to appeal, officials said.

Those aboard included Mairead Corrigan, who won the 1976 Nobel Peace Prize for her work with Catholics and Protestants in Northern Ireland, and the former UN humanitarian co-ordinator in Iraq, Denis Halliday.

Sabine Haddad, spokeswoman for the Israeli Interior Ministry, said that all 19 were being held at Israel's international airport Saturday night, and that eight agreed to leave voluntarily on Sunday. The remaining activists, including Corrigan and Halliday, were challenging the deportations, though Haddad said she expected some of them to change their mind and leave voluntarily.

Netanyahu fears 'Iranian port'

After the latest takeover at sea, Israeli Prime Minister Benjamin Netanyahu signalled he is determined to enforce the naval blockade, saying he would "not allow the establishment of an Iranian port in Gaza."

Iran is one of Israel's most implacable foes and supplies weapons and cash to Hamas.

Netanyahu said Israel's three-year-old blockade of Gaza is meant to keep weapons out of the hands of Hamas.

Egypt has helped enforce the blockade on land, but President Hosni Mubarak ordered the passenger terminal with Gaza to open daily, instead of sporadically, after last Monday's raid.

The U.S. had adopted a gradual approach of persuading Israel to ease restrictions but said Friday it was working "urgently" with Israel, the Palestinian Authority and other international partners to develop new procedures for delivering more goods to Gaza while blocking the entry of weapons.

With files from The Associated Press