German prosecutors said Wednesday they had formally charged a known neo-Nazi with the June 2019 murder of a pro-refugee politician, the first in a string of recent far-right killings.

Federal investigators said 45-year-old Stephan Ernst drove to Walter Luebcke's house in Wolfhagen, central Germany, on the evening of June 1, 2019.

He crept up under cover of darkness to the terrace where Luebcke sat before shooting him in the head with a revolver.

Ernst's "racism and xenophobia founded on an ethnic-nationalist attitude were decisive in the act," prosecutors said in a statement.

The suspect and his fellow accused, identified only as Markus H., had attended a political meeting in October 2015 where Luebcke argued in favor of accommodating refugees in the town of Lohfelden.

Ernst "from the time of the meeting increasingly projected his xenophobia onto Dr. Walter Luebcke," a regional politician from Chancellor Angela Merkel's center-right CDU party, prosecutors said.

At the time of his June 2019 arrest, the main suspect in Luebcke's killing held "several firearms and ammunition that he had acquired illegally," prosecutors said, including three revolvers, two automatic pistols, two rifles, 1,400 rounds of ammunition and a submachine gun.

Arrested soon afterwards, H. was found to be in possession of a deactivated submachine gun.

After the arrests, Ernst had initially confessed to Luebcke's murder, but in January this year he retracted the admission and said H. had shot the politician.

But prosecutors remain convinced that while H. "accepted and supported" the danger Ernst posed, he "was not familiar with the actual plans for the attack."

The killing was followed by an October attack on a synagogue in eastern city Halle that left two dead, while a gunman shot dead nine people of migrant backgrounds in central town Hanau in February.

Perpetrators in both attacks posted racist screeds online, and Interior Minister Horst Seehofer has since declared far-right extremism the "biggest security threat facing Germany," promising a beefed-up security response.