BARCELONA, Oct 3, 2025 (BSS/AFP) - Thousands of people marched through the streets of Barcelona on Thursday to denounce Israel's interception of a pro-Palestinian aid flotilla bound for Gaza.

Columns of demonstrators, many waving Palestinian flags, converged on the central Plaza de les Drassanes from multiple parts of Spain's second-largest city.

Protesters chanted slogans including "Gaza, you are not alone", "Boycott Israe," and "Freedom for Palestine."

About 15,000 people took part, according to Barcelona's municipal police force, the Guardia Urbana.

Around 10,000 people took part in a similar protest in Madrid, local officials said. Protests were held in other Spanish cities Thursday night including Bilbao, Seville and Valencia.

As the Barcelona march reached a highway entrance, riot police formed a line to block the crowd.

When some protesters attempted to climb over barriers, officers responded with truncheon strikes, forcing the front lines to retreat, images broadcast on Spanish public television showed.

The Global Sumud Flotilla, with around 45 vessels carrying politicians and activists, departed Barcelona last month to challenge Israel's blockade of Gaza, where the United Nations reports famine conditions after nearly two years of war.

The Israeli navy intercepted several vessels at sea beginning Wednesday, after warning activists against entering waters it says fall under its blockade.

A boat carrying former Barcelona mayor Ada Colau was among those prevented from proceeding.

Spain's Foreign Minister Jose Manuel Albares said he had summoned Israel's top diplomatic representative in Madrid to discuss the situation, adding that 65 Spaniards were travelling with the flotilla.

Spain's public prosecutor's office said it would collect information on the interception as part of an ongoing probe into alleged Israeli military human rights abuses in Gaza.