BERLIN—The leader of a small faction of German extremists was seriously injured Thursday while trading gunfire with police as he and supporters tried to prevent an eviction order being served on the house he was living in.

Two police commandos received minor injuries.

Adrian Ursache, 41, a member of the Reichsburger movement, which rejects the German government as illegitimate, exchanged fire with special police commandos in a village near Leipzig, an official familiar with the situation said. He was later taken by helicopter to a hospital, where he was in stable condition, the official said.

The Reichsbürger movement, which translates as “citizens of the empire” and includes different factions across the country, rejects the modern German Federal Republic and believes that the German Empire still exists as defined by its borders from the 1930s. Members have refused to pay tax, resisted law enforcement and refused to carry official identification documents.

Around 200 special police commandos and state riot police arrived at the house of Mr. Ursache, a 1990s “Mr. Germany” pageant winner, on Thursday morning to help court marshals execute an eviction notice stemming from unpaid debt on the property.