Eight people have been wounded in a knife attack in the Russian city of Surgut, security sources say.
The man, who apparently stabbed passers-by on the street at random, was shot dead by police.
The injured have been taken to hospital, where two are in a critical condition, the state-owned RIA Novosti news agency reports.
Russia’s Investigations Committee said the attacker had been “liquidated”. No motive has been established yet.
The TASS news agency quoted local police as saying the man may have been suffering from mental illness.
A spokeswoman for the investigating committee told Reuters news agency she would not comment on the possibility of terrorist motives, calling the attack “attempted murder”.
News outlet Russia Today reported the attack happened at about 11:20 local time (06:20 GMT).
Surgut, about 2,100km (1,300 miles) east of Moscow in the Khanty-Mansiysk area of Siberia, has a population of more than 350,000.