BERLIN—The German daily Die Welt is reporting that police have foiled a knife attack on a half-marathon in Berlin.

The paper says special police forces detained four men in connection with Sunday’s sports event. They said the main suspect was planning to kill participants and spectators with knives.

German news agency dpa reported that police confirmed arrests in connection with the half-marathon but gave no further details.

According to Die Welt, the main suspect knew Anis Amri, the Tunisian attacker who killed 12 people and injured dozens when he drove a truck into a Christmas market in Berlin in December 2016.

The paper reported that the suspect, who was not identified, had prepared extra-sharpened knives to use in the attack.

German police confirmed some arrests in Berlin on Sunday.