The Global Sumud Flotilla set sail last month, ferrying politicians and activists including Swedish campaigner Greta Thunberg towards Gaza, where the United Nations says famine is taking hold.

The Israeli navy began intercepting the boats on Wednesday, and an Israeli official said the following day that boats with over 400 people on board had been prevented from reaching the Gaza Strip.

Israel said it would deport the activists to Europe, adding that none of the vessels had breached its maritime blockade of the territory.

"Marinette, the last remaining boat of the Global Sumud Flotilla, was intercepted at 10:29 am (0729 GMT) local time, approximately 42.5 nautical miles from Gaza," the flotilla organizers said on Telegram. 

The statement added that Israeli naval forces had "illegally intercepted all 42 of our vessels -- each carrying humanitarian aid, volunteers, and the determination to break Israel's illegal siege on Gaza".

The interception of the final boat, which brings to an end this flotilla's mission, came hours after protesters around the world held rallies condemning Israel's actions.

About 15,000 people marched in Barcelona in Spain, where the flotilla began its voyage, chanting slogans including "Gaza, you are not alone", "Boycott Israel" and "Freedom for Palestine".

Hundreds also gathered outside the Irish parliament in Dublin, where Miriam McNally, whose daughter was sailing with the flotilla, said she was "worried sick".

Protests also took place in Paris, Berlin, The Hague, Tunis, Brasilia and Buenos Aires, according to AFP correspondents.

Israel has branded some of the activists, including Thunberg, as antisemitic, and Prime Minister Benjamin Netanyahu praised the navy's interception efforts.

"I commend the soldiers and commanders of the navy who carried out their mission on Yom Kippur in the most professional and efficient manner," he said in a statement Thursday. 

"Their important action prevented dozens of vessels from entering the war zone and repelled a campaign of delegitimization against Israel."

Gaza's civil defense agency and hospitals said Israeli strikes on the territory killed at least 52 people on Thursday, including an employee of the French charity Doctors Without Borders.

The nearly two-year war was sparked by Palestinian militant group Hamas's unprecedented attack on Israel on October 7, 2023.

The attack resulted in the deaths of 1,219 people, mostly civilians, according to an AFP tally based on official Israeli figures.

Israel's retaliatory military campaign since then has killed 66,225 Palestinians in Gaza, also mostly civilians, according to figures from the Hamas-run health ministry, which the United Nations considers reliable.