BARCELONA (AP) — A flotilla of ships departed from Barcelona to the Gaza Strip Sunday with humanitarian aid and activists on board in the largest attempt yet to break the long Israeli blockade of the Palestinian territory by sea.

This comes as Israel has stepped up its offensive on Gaza City, limiting the deliveries of food and basic supplies in the north of the Palestinian territory. Food experts warned earlier this month that the city was in famine and that half a million people across the strip were facing catastrophic levels of hunger.

The Global Sumud Flotilla is carrying food, water and medicine. Activists on board demanded safe passage to deliver the much-needed aid and the opening of a humanitarian sea corridor, according to a statement. The almost 23-month war has killed more than 63,000 people, with at least 332 Palestinians dying of malnutrition, including 124 children, according to the Gaza Health Ministry.

The maritime convoy of about 20 boats and delegations from 44 countries is claimed to be the largest attempt to date to break the Israeli blockade of the Gaza Strip by sea, which has now lasted 18 years. They will be joined by more ships from ports in Italy and Tunisia in the coming days, on the route from the western end of the Mediterranean to the Gaza Strip, organizers said.

Thousands of supporters flocked to the Barcelona pier, some of them wearing kaffiyehs and chanting “Free Palestine!” and “Boycott Israel!” to send off a wide variety of boats, flying Palestinian flags, from rundown old luxury yachts to tiny wooden sailboats and industrial-looking vessels. One of them, the Sirus, is more than 100 years old.

Around 70 boats are expected to take part in the final leg of the journey, flotilla spokesperson Saif Abukeshek told Spanish public television after the departure. The fleet could reach Gaza around Sept. 14 or 15, he added.

“The story here is about Palestine. The story here is how people are being deliberately deprived of the very basic means to survive,” said Swedish activist Greta Thunberg at a news conference. She is one of the most recognizable figures on the expedition, formed by hundreds of activists, politicians such as the former mayor of Barcelona, Ada Colau, and journalists.

Ships carrying tons of humanitarian aid departed from the Italian city of Genoa and will join the expedition in the coming days.

It is not the first time Thunberg has attempted to reach Gaza waters this year. She was deported by Israel in June when the ship she was traveling on with 11 other people, the Madleen, was stopped by the Israeli military.

“It has been very clear that Israel has been continuously violating international law by either attacking, unlawfully intercepting the boats in international waters, and continuously preventing the humanitarian aid from coming in,” said Thunberg in an interview with The Associated Press on Saturday.

The Global Sumud Flotilla will be the fourth attempt to break the maritime blockade so far this year. The Conscience first tried in May, but was attacked by drones after setting sail from Malta. After the Madleen, the Israeli military stopped another aid ship, the Handala, in late July, detained 21 international activists and reporters and seized its cargo, including baby formula, food and medicine, according to the Freedom Flotilla Coalition.

In a news conference before the departure in Barcelona, actor Liam Cunningham played a video showing a girl singing while planning her own funeral. The girl, Fatima, died four days ago, he said.

“What sort of world have we slid into where children are making their own funeral arrangements?” Cunningham told reporters.

An Israeli official said Saturday that the country will soon halt or slow humanitarian aid into parts of northern Gaza, as it expands its military offensive against Hamas, a day after the city was declared a combat zone.

The war began on Oct. 7, 2023, when an attack by Hamas militants inside Israel claimed the lives of 1,200 people, most of them civilians, and took 251 people hostage.

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This story has been corrected to reflect that actor Susan Sarandon was not part of the crew aboard the boats.

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Medrano reported from Santiago, Spain.