The October 2024 floods caused significant damage and claimed 235 lives nationwide, Spain's deadliest such disaster in decades. Most of the deaths were in the eastern Valencia region, where popular fury targeted officials in the aftermath.

The disinformation campaign by pro-Russian activists exploited the floods to fuel public distrust in state institutions, the Department of National Security report said, according to the Barcelona-based newspaper.

The report said they spread messages claiming that Socialist Prime Minister Pedro Sanchez's government was diverting public funds to support Ukraine in the wake of Russia's invasion at the expense of "Spain's real need for aid", it added.

The Department of National Security, an advisory body in the prime minister's office that focuses on threats such as terrorism and cyberattacks, did not make its report publicly available and AFP was unable to access it.

Pro-Russian groups also intensified their disinformation campaigns ahead of the European Parliament elections in June 2024 in an effort to undermine trust in the electoral system, the report said.

The European Union warned in March that Russia and China were using "massive digital arsenals" to interfere in Western democracies, while their messaging around the war in Ukraine had become increasingly aligned.

The EU has grown more concerned about Russian interference as part of what it sees as a broader hybrid campaign from Moscow that includes sabotage attacks to weaken the West.

Brussels imposed its first sanctions on Russian intelligence operatives in December over the alleged malign activities.

False claims spread rapidly online following Spain's floods, with some posts -- often shared on platforms linked to Russia -- alleging the government was hiding the true number of victims.

Other unfounded reports falsely blamed dam failures for the flooding and warned, without evidence, of contaminated drinking water in the Valencia region.

Against this backdrop, furious locals hurled mud and insults at Sanchez, King Felipe VI and Queen Letizia in November 2024 when they visited one of the worst-hit towns in a startling show of anger.