Organisers of eight-ship fleet predict standoff as they attempt to cross into 20-mile exclusion zone off coast

The Israeli navy was today preparing to confront a flotilla of eight ships carrying hundreds of pro-Palestinian activists and 10,000 tons of aid which is attempting to break the Israeli blockade of the Gaza Strip.

The flotilla is expected to head towards the Gaza coastline tomorrow. The Israeli military has declared its intention to block the flotilla's progress as soon as it attempts to cross from international waters into the 20-mile exclusion zone Israel maintains off Gaza's coast.

The military declined to confirm a report in the Israeli daily Ma'ariv detailing a five-point plan for the confrontation, including warnings, takeover by force, and the detention and deportation of the activists on board.

A temporary detention centre has been established in the Israeli port of Ashdod, 23 miles north of Gaza City, where officials will reportedly offer activists the choice between immediate deportation to their country of origin or being bussed to jails across the country while a legal process to expel them takes its course.

Greta Berlin of the Free Gaza Movement, one of the organisations behind the flotilla, indicated today that most of those on board would refuse to comply with the Israeli authorities.

She said: "We are committed to getting into Gaza. We expect a standoff at sea."

The activists were braced for a violent confrontation, said Berlin, pointing to a previous incident in December 2008 when a similar attempt to reach Gaza by sea ended in the activists' boat being rammed by the Israeli navy.

She claimed the navy was attempting to stop the eight boats converging into a flotilla by threatening to attack one of their number, a Turkish passenger ship carrying around 650 people. "They're going to try to pick us off one by one," she said. Israel had jammed satellite phones and radars on board the ships, she claimed.

However, an Israeli military spokesman said there had been no contact between the navy and the activists. "We're waiting to see what happens – it depends on how things proceed," he said.

The Ma'ariv report said the military feared that there could be "terror activists", explosives and weapons on board the ships.

Berlin denied this, saying every item on board each ship had been inspected by port authorities and manifests issued. "Yet the Israelis are coming towards us armed to the teeth."

As well as the prospect of a physical confrontation, a propaganda war between Israel and the activists was well under way today.

Avigdor Lieberman, Israel's foreign minister, said the flotilla was "an attempt at violent propaganda against Israel, and Israel will not allow a violation of its sovereignty at sea, in the air, or on land."

He added: "There is no humanitarian crisis in Gaza, and despite the Hamas leadership's war crimes and rocket fire, Israel is conducting itself in the most humanitarian manner, and is allowing the entrance of thousands of tons of food and equipment into Gaza."

However, the UN and other aid organisations have repeatedly pointed to the devastating impact of the acute shortage of construction materials to rebuild homes and infrastructure following the 2008-9 war, as well as restrictions on foods, medical equipment and school supplies allowed into Gaza.