Spain has "urgently" called in Israel's charge d'affaires in Madrid to express its "strongest condemnation" over the detention of activists, including Spanish nationals, from the Global Sumud humanitarian aid flotilla, according to Spanish news agency EFE, News.Az reports.

Sources from Spain’s foreign ministry said on Thursday that embassies and consulates in Israel and the region, along with the consular emergency unit, were “fully operational and in contact with the organisers of the flotilla.”

The ministry said that Foreign Minister Jose Manuel Albares was also in contact with counterparts from other countries whose citizens were among those arrested.

One of the crew members, Catalan firefighter Pau Perez, who was not arrested, said on social media that they had spent the night trying to evade Israeli vessels.

“We do not know where they have taken them,” Perez said, according to EFE, calling for protests to demand their release.

Sources in the aid flotilla said, according to the report, that about 20 of those Spanish nationals reside in Catalonia.

The flotilla, which consists of 58 vessels carrying activists from multiple countries, departed Barcelona on April 15, aiming to break the blockade on Gaza and deliver humanitarian aid.