Hundreds of activists, including Swedish climate campaigner Greta Thunberg, have been detained by Israeli forces after a flotilla carrying aid bound for Gaza was intercepted.

Israel’s Foreign Ministry said those involved in the Global Sumud Flotilla (GSF) were being transferred to an Israeli port to be deported.

The first boats were stopped about 70 nautical miles off the Gaza coast in international waters and others closer. Israel has been policing this area but does not have jurisdiction there.

Israel said its navy told the boats to change course as they were “approaching an active combat zone and violating a lawful naval blockade”, while the GSF described the interceptions as “illegal”.

The group said Israel’s response was “not an act of defence”, but “a brazen act of desperation”.

It estimated 443 people were detained from the boats and alleged that many were assaulted with water cannon. Israel said all those detained were “safe and in good health”.

A growing number of countries have expressed concern over the incident, criticising Israel for staging the interception in international waters.

Colombian President Gustavo Petro has expelled all remaining Israeli diplomats from the country in response, and denounced the interception as an “international crime by [Israel’s Prime Minister] Netanyahu”.

Petro also terminated Colombia’s free trade agreement with Israel, in place since 2020, and called for the release of two Colombians who were aboard the flotilla.

Amnesty International’s Secretary General, Agnès Callamard, said Israel’s blockade on Gaza was “unlawful” and that the “decades-long impunity for Israel’s blatant violations of international law must end”.

However, Italy’s Prime Minister Giorgia Meloni criticised the attempt to reach Gaza, saying: “I continue to believe that all this brings no benefit to the Palestinian people.”

Israel’s Foreign Ministry posted footage from the interception showing Thunberg sitting on the deck of a boat, being handed water and a jacket by a member of the Israeli military. Detained activists are being taken to the port of Ashdod, Israel said.

“Greta and her friends are safe and healthy,” the Israeli government said.

Israel has described the flotilla as “provocation yachts” and contends that it was justified in stopping the vessels before they entered the naval blockade of the waters that border Gaza.

It said one boat remained “at a distance” and would be intercepted if it approached the blockade.

That boat appeared to be the Marinette, which the GSF said was still in communication and carrying six people on board. The flotilla’s tracking system showed it sailing in international waters a long distance from Gaza’s coastline on Thursday afternoon.

Israel said none of the boats entered the blockade area, though the GSF tracking suggests one of its boats, the Mikeno, may have entered Gaza’s territorial waters, but remains out of contact.

A member of the legal team working with the flotilla has said there will be a further attempt to breach Israel’s blockade “in the coming days”.

Caoimhe Butterly, who is aboard a vessel providing legal support and acting as an observer to the GSF, said: “There is the expectation that it will be up to 13 vessels, ships and boats and that it will follow a similar route to Gaza.”

People have gathered in Greece, Italy, Germany, Tunisia and Turkey to protest against Israel’s interception of the flotilla. Its actions have also drawn criticism from Pakistan, Bolivia and Malaysia.

In Italy, spontaneous rallies took place in some cities on Wednesday evening. Its main trade union CGIL confirmed it was backing a general strike on Friday in solidarity with Gaza and in response to what it said was the “abandonment” of Italian workers “in open international waters” by the Italian government.

The flotilla had been accompanied by Italian and Spanish naval vessels following alleged drone attacks and communications jamming of unclear origin, but these peeled away well before the interception began.

The UN High Commissioner for Human Rights, Volker Türk, called for Israel to “urgently lift the blockade on Gaza and allow the entry of life-saving material through all means possible”, adding in a statement that it must agree to facilitate impartial humanitarian relief schemes “without hindrance”.

The UK Foreign Office said it had been in contact with the families of the British nationals aboard the boats, adding that it had contacted Israeli authorities to “make clear we expect the situation to be resolved safely”.

Irish Deputy Prime Minister Simon Harris called the reports “concerning” and said he expects Israel to uphold international law, with at least seven Irish citizens among the detained, including Sinn Féin Senator Chris Andrews.

The flotilla left Spain a month ago, with more than 40 ships and around 500 people aboard, including European parliamentarians, lawyers and activists, with the stated intention of taking aid directly into Gaza.

Israel has already blocked two attempts by activists to deliver aid by ship to Gaza, in June and July.

While the Israeli government has characterised the flotilla as a “selfie yacht”, Thunberg has pushed back against that criticism, telling the BBC on Sunday: “I don’t think anyone would risk their life for a publicity stunt.”

International aid agencies have been attempting to get food and medicine into the Palestinian territory but say Israel is restricting the flow of supplies.

Israel claims it is attempting to stop those supplies falling into the hands of Hamas. It and the US have backed an alternative food distribution system, the Gaza Humanitarian Foundation (GHF), which the UN has branded unethical and “inherently unsafe”.

The Integrated Food Security Phase Classification (IPC), a UN-backed group considered an impartial expert body, confirmed last month that there was famine in Gaza, and the UN’s humanitarian chief said it was the direct result of Israel’s “systematic obstruction” of aid entering the territory.

Netanyahu has called this an “outright lie”, rejecting the evidence presented by the IPC.