A flotilla of ships departed from Barcelona to the Gaza Strip Sunday with humanitarian aid, activists and celebrities on board seeking to break the Israeli blockade of the Palestinian territory.

The departure comes as Israel has stepped up its offensive on Gaza City, limiting 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, Greece 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!”

A wide variety of boats, flying Palestinian flags, were waiting to set sail, from run-down old luxury yachts to tiny wooden sailboats and industrial-looking vessels.

One of them, the Sirus, is more than 100 years old.

Greta Thunberg is one of the most recognizable figures on the expedition, alongside actors Susan Sarandon and Liam Cunningham, as well as activists, politicians like former mayor of Barcelona, Ada Colau, and journalists.

It is not the first time Thunberg has attempted to reach Gaza waters this year.

She was deported in June when the ship she was traveling on with 11 other people, the Madleen, was stopped by the Israeli military.

In late July, the Israeli military stopped another aid ship, detained 21 international activists and reporters and seized its cargo, including baby formula, food and medicine, according to Freedom Flotilla Coalition.

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.