The return of activists from the Gaza flotilla to Bilbao, Spain, over the weekend turned violent, as police used batons against both the activists and demonstrators who had gathered at the airport to welcome them.

The incident occurred when supporters assembled in the arrivals hall to greet six activists returning to the Basque Country on a flight from Turkey, after having been detained by Israeli forces.

Earlier, activists had reportedly blocked the exit for other passengers, and police attempted to remove them.

Four people were arrested for serious disobedience, resisting authority, and assaulting police officers, according to a statement by the Basque regional police. Two of those arrested were activists who had just returned from Turkey.

“Following the events at the airport, the Police Internal Affairs Unit launched an investigation to determine whether the officers’ conduct complied with established procedures,” the statement said.

At the same time, the Israeli embassy in Spain sarcastically demanded “explanations” from the Spanish government regarding the events at Bilbao airport.

After the clashes, around 2,000 demonstrators took to the streets of Bilbao on Sunday to condemn the treatment of the activists by the Basque police. During the march, pro-Palestinian protesters carried anti-Israel banners criticizing the Basque police and accusing the local government of “complicity with Zionism.”

The incident occurred while Spain was among the Western governments that expressed outrage on Thursday following the release of a video by Israeli minister Itamar Ben-Gvir, in which he mocked the activists while they were restrained on the ground inside a prison at the port of Ashdod.

At the same time, comparisons between videos of the activists leaving Israel and arriving in Turkey have gone viral. The reason is that the activists attempted to portray themselves as having been physically abused during their time in Israel. Upon arriving in Turkey, they were seen on stretchers, whereas footage from their departure from Israel showed them appearing healthy and walking without any apparent difficulty.