Berlin police tweeted that the six were being detained in cooperation with the city’s prosecutor’s office. The main suspect, who was not identified, had two knives he was going to use for the attack.
Police had raided apartments and two vehicles in the Charlottenburg and Neukoelln districts of the city.
A German newspaper gave a different account. Special police forces detained “four men” in connection with the race plot, before the race started on Sunday, Die Welt reported.
The German daily first reported that police had discovered a terror plot to attack race spectators and participants with knives. The main suspect is an acquaintance of Anis Amri, the Tunisian terrorist who killed 12 people and injured dozens more when he drove a truck into a Christmas market in Berlin in December 2016.
Berlin police raided the same apartment that they had searched after the Christmas market attack, according to the newspaper.
“There were isolated indications that those arrested, aged between 18 and 21 years, were participating in the preparation of a crime in connection with this event,” prosecutors and police said in a joint statement.
According to local daily Tagesspiegel, the main suspect had been under observation for two weeks around the clock. A foreign intelligence service had tipped off German authorities that he was planning to attack the half-marathon.
The half-marathon was being guarded by some 630 police officers, German news agency dpa reported.