FRANKFURT AM MAIN, Germany — German police on Thursday raided sites across the country linked to a far-right group banned by the interior ministry, weeks after a suspected extremist gunman shot dead nine people of migrant backgrounds.

Germany’s top security official, Horst Seehofer, issued a ban on the United German Peoples and Tribes, the first time a group associated with the so-called Reichsbuerger movement has been proscribed.

“We are dealing with a group that distributes racist and anti-Semitic writings and in doing so systematically poisons our free society,” Seehofer said in a statement.

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The Interior Ministry said around 400 police officers had seized firearms, propaganda material and small amounts of drugs during the raids on the homes of 21 leading members of the group.

“Since the early hours, police measures are going on in ten states” out of Germany’s 16, interior ministry spokesman Steve Alter wrote on Twitter.

Authorities say members of the newly banned group, whose activities were focused in Berlin, had issued threats against German officials.

The “United German Peoples and Tribes” organization banned Thursday belongs to a wider “Citizens of the Reich” movement fed by conspiracy theories.

Reichsbuerger have similarities to the sovereign citizens movements in the United States and elsewhere. They reject the authority of the modern German state and promote the notion of “natural rights,” often mixing this ideology with far-right politics and esoteric conspiracy theories.

Its adherents have in the past entered into armed confrontations with police.

In a 2016 shootout, a Reichsbuerger-linked man killed an officer and wounded two more.

He was later sentenced to life in prison.

After a racist gunman shot dead nine people of migrant backgrounds in the city of Hanau last month, Seehofer declared far-right extremism “the biggest security threat facing Germany” and announced increased police measures.

Seehofer said the far right had left “a trail of blood” in recent months — two people died in an attack on a synagogue in the city of Halle in October and a pro-migrant politician was murdered at his home in June.

The Hanau shooter, identified in news reports as Tobias R., reportedly said he wanted to exterminate people from Asia, North Africa and Israel.

Separately, 12 men were arrested across Germany in February on suspicion of planning attacks on mosques aimed at bringing about “a civil-war-like situation.”

The government has announced hundreds of new posts for federal police and security services to strengthen surveillance of the far-right scene, and is considering tighter laws on gun ownership.