JERUSALEM — Israeli forces seized a Gaza-bound aid boat and detained Greta Thunberg and other activists who were on board early Monday, enforcing a longstanding blockade of the Palestinian territory that has been tightened during the war with Hamas.

The activists had set out to protest Israel’s ongoing military campaign in the Gaza Strip, which is among the deadliest and most destructive since World War II, and its restrictions on the entry of humanitarian aid, both of which have put the territory of some 2 million Palestinians at risk of famine.

The Freedom Flotilla Coalition, which had organized the voyage, said the activists were “kidnapped by Israeli forces” while trying to deliver desperately needed aid to the territory.

“The ship was unlawfully boarded, its unarmed civilian crew abducted, and its life-saving cargo – including baby formula, food and medical supplies – confiscated,” it said in a statement. It said the ship was seized in international waters some 200 kilometers (120 miles) from Gaza.

Israel’s Foreign Ministry portrayed the voyage as a public relations stunt, saying in a post on X that “the ‘selfie yacht’ of the ‘celebrities’ is safely making its way to the shores of Israel.” The boat was expected to arrive at the Israeli port of Ashdod later on Monday.

The Foreign Ministry said the activists would return to their home countries and the aid would be sent to Gaza through established channels. It circulated footage of what appeared to be Israeli military personnel handing out sandwiches and water to the activists, who were wearing orange life vests.

A weeklong voyage

Thunberg, a climate campaigner, was among 12 activists aboard the Madleen, which set sail from Sicily a week ago. Along the way, it had stopped on Thursday to rescue four migrants who had jumped overboard to avoid being detained by the Libyan coast guard.

“I urge all my friends, family and comrades to put pressure on the Swedish government to release me and the others as soon as possible,” Thunberg said in a pre-recorded message released after the ship was halted.

Rima Hassan, a French member of the European Parliament who is of Palestinian descent, was also among the volunteers on board. She has been barred from entering Israel because of her opposition to Israeli policies toward the Palestinians.

After a 2-month total blockade aimed at pressuring Hamas, Israel started allowing some basic aid into Gaza last month, but humanitarian workers and experts have warned of famine unless the blockade is lifted and Israel ends its military offensive.

An attempt last month by Freedom Flotilla to reach Gaza by sea failed after another of the group’s vessels was attacked by two drones while sailing in international waters off Malta, organizers said. The group blamed Israel for the attack, which damaged the front section of the ship.

An 18-year blockade

Israel and Egypt have imposed varying degrees of blockade on Gaza since Hamas seized power from rival Palestinian forces in 2007. Israel says the blockade is needed to prevent Hamas from importing arms, while critics say it amounts to collective punishment of Gaza’s Palestinian population.

Israel sealed Gaza off from all aid in the early days of the war ignited by the Hamas-led attack on southern Israel on Oct. 7, 2023, but later relented under U.S. pressure. In early March, shortly before Israel ended a ceasefire with Hamas, the country again blocked all imports, including food, fuel and medicine.

Hamas-led militants killed around 1,200 people, mostly civilians, in the Oct. 7 attack and abducted 251 hostages, most of whom have since been released in ceasefire agreements or other deals. Hamas is still holding 55 hostages, more than half of them believed to be dead.

Israel’s military campaign has killed more than 54,000 Palestinians, according to the Gaza Health Ministry, which doesn’t distinguish between civilians and combatants but has said women and children make up most of the dead.

The war has destroyed vast areas of Gaza and displaced around 90% of the territory’s population, leaving people there almost completely dependent on international aid.

Efforts to broker another truce have been deadlocked for months. Hamas says it will only release the remaining hostages in exchange for a lasting ceasefire and an Israeli withdrawal, while Israel has vowed to continue the war until all the captives are returned and Hamas is defeated or disarmed and exiled.