German federal prosecutors said Thursday they have taken over the case of a suspected far-right extremist accused of leading online groups that preyed on minors and incited killings, arson and severe acts of self-harm across several countries.

Kai M., who is under 20 and was arrested March 17, remains in pretrial detention and is suspected of acting as a ringleader in two organizations that prosecutors have described as criminal and terrorist groups influenced by far-right ideology.

Authorities allege Kai M. and other members manipulated young people online into committing violent crimes, including inducing a minor in Russia to fatally stab another child at a school.

The suspect is also accused of calling for the killing of a U.S. citizen in an online chat and influencing young people in the U.S. and Sweden to set vehicles on fire.

In another case cited by prosecutors, Kai M. allegedly contacted a child in another European country online and coerced the victim into performing sexual acts involving a knife, resulting in serious injuries.

Investigators believe one of the groups sought to provoke serious crimes, including murder and manslaughter, as part of an effort to destabilize society and ultimately bring about the collapse of the existing social order. Kai M. is also suspected of distributing videos depicting crimes that he allegedly helped instigate.

Both groups are linked to the so-called "Com" scene, a loose international network of online communities in which members glorify violence and target vulnerable young people, according to prosecutors.

Members allegedly approach children and teenagers through social media and gaming platforms before using manipulation, grooming, coercion and extortion to push them into humiliating acts, self-harm, violence or suicide.

The case highlights growing concern over a violent online subculture authorities have associated with nihilistic violent extremism, in which perpetrators seek both to exploit vulnerable victims and encourage acts intended to spread fear and social disorder.

The allegations bear similarities to a separate German case involving a 21-year-old German-Iranian man known online as "White Tiger." The suspect, identified under German privacy rules as Shahriar J., is accused of a series of sadistic online offenses, including coercing a 13-year-old into suicide.

His trial began at a juvenile court in Hamburg in January and is scheduled to continue through December.

Kai M. was detained on a warrant issued by a court in Koblenz. He is expected to appear before an investigating judge at Germany's Federal Court of Justice as federal prosecutors assume responsibility for the case.