(CNN) A man was fatally shot by police Saturday after he attacked four bystanders with a knife at a metro station in Iran's capital, Tehran, state media reported.

Police said four people were injured by the 40-year-old assailant, according to Iran's Islamic Republic News Agency.

Security forces at the station asked the attacker to hand over his weapon but he refused, forcing them to open fire, injuring him in the leg, IRNA cited the police information center in Tehran as saying. He died from his injuries on the way to the hospital.

"The incident is a singular one and has no terrorist background," IRNA quoted police as saying.

The attack occurred at the Shahr-e-Rey metro station south of Tehran.

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