A German man who boasted that he had supplied the firearm used by a gunman who killed nine people in Munich last month has been arrested, the Frankfurt state prosecutor has said.
The 31-year-old was detained in Marburg, about 100 km north of Frankfurt, after authorities contacted him on the so-called "dark net" posing as buyers for an automatic weapon and a Glock 17 pistol for 8,000 euros.
The man's claims were supported by evidence gathered by the Munich prosecutor's office and Bavarian state police, the statement said.
Bavarian state police said there is "strong evidence" that the 31-year-old man sold the Glock 17 used in the Munich shooting to 18-year-old German-Iranian David Ali Sonboly shortly before the attacks.
The suspect was identified during unrelated investigations into illegal weapons purchases.
During the subsequent sting operation, the suspect said he had sold the 18-year-old the Glock 17 pistol during a meeting in Marburg on May 20, followed by 350 rounds of ammunition during a second meeting on July 18, according to the statement.
The gunman then went on to kill nine people in Munich on July 22, then shot himself.