The 45-year-old suspect, identified only as Stephan E. in line with privacy laws, is accused of killing Walter Luebcke, 65, with a pistol shot to the head earlier this month, Markus Schmitt, a spokesman for Germany's federal prosecutor's office, said.
"We believe that the crime was motivated by right-wing extremism," Schmitt told reporters in Karlsruhe. Investigators came to that conclusion based upon the suspect's publicly expressed political views and past actions, he said. At the moment, there are no indications Stephan E. was a member of any right-wing terrorist organization, Schmitt said, adding investigators were still trying to determine if there were any others involved in the crime.
Schmitt took no questions from reporters. Germany's Die Zeit newspaper reported the suspect had a history of involvement in hate crimes dating back decades, including a 1993 pipe bomb attack on a refugee shelter in Germany's Hesse state.
Merkel later said she had confidence that all details would be "intensively looked into." "I hope that we will soon have complete clarity," she said. Luebcke was killed June 2 at his home near the central German city of Kassel. Hundreds of people attended his burial Saturday, and some 1,300 attended a memorial service last week.
A member of Merkel's Christian Democratic Union party, Luebcke ran the Kassel area regional administration and had publicly supported the chancellor's approach to welcoming refugees who reached Europe in large numbers several years ago.
Hesse state police and prosecutors set up a task force of 50 investigators to look into Luebcke's slaying. Stephan E. was arrested Saturday. They said his DNA matched evidence at the crime scene. Federal prosecutors took over the case due to the "particular significance" of the crime, Schmitt said. Investigators are now evaluating digital storage devices seized during E.'s arrest.
German President Frank-Walter Steinmeier said a thorough investigation should be the "highest priority." Stephan Thomae, a federal lawmaker with the opposition Free Democrats, called for a parliamentary committee to look into the case.
"Right-wing extremists who call for acts of violence, or who carry them out, must feel the full severity of the law," Thomae said. "It is totally unacceptable for people in our country to be threatened or murdered over political statements and decisions."
Frank Jordans contributed to this story.