A man armed with a knife has injured seven pedestrians in the Russian city of Surgut. Police killed the assailant as he was resisting arrest and are investigating claims he was mentally ill. Meanwhile, terrorist group Islamic State claimed responsibility for the attack.

The knife attacks happened at around 11:20am local time. Nobody was killed, but the victims of the violence required medical treatment, the Investigative Committee said. Law enforcement initially reported the number of victims as eight, but corrected the statement later.

The attacker was shot dead by a police patrol responding to the emergency reported by witnesses. The man resisted an attempt to arrest him even after a warning shot was fired in the air, the report said.

The attacker was identified as a Surgut resident in his early 20s. The Surgut police are trying to establish the motive for his stabbing spree. Investigators are currently trying to verify a claim that the attacker suffered from a mental illness, the police said.

Investigators do not view terrorism as a primary possible motive at the moment, the local police press service told Interfax.

However, Islamic State claimed credit for the attack, Reuters reports, citing the terrorist group’s Amaq news agency.

Surgut is the largest city and provincial capital of the Khanty-Mansi Autonomous Area, east of the Ural Mountains. It has a population of over 360,000 and remains a major center for oil and gas production in Russia.

These images were posted on Russian social media, showing scenes of the violence in Surgut.