According to the Investigative Committee, "an unidentified man ran along the city's central streets and stabbed pedestrians, injuring eight".
Regional authorities are assisting the injured, of whom two are in critical conditions, local health authorities said.
The attack began around 11:20 a.m.in Surgut, a city in northern Russian Federation. Although Russian news outlets reported the attack wasn't terror related, ISIS later claimed responsibility for the attack.
Islamic State says the man - shot dead by police - was a "soldier" of the extremist group.
A spokeswoman for the committee told Reuters news agency she would not comment on the possibility of terrorist motives, calling the attack "attempted murder".
Russia's Investigations Committee said the attacker had been "liquidated".
The statement gave the number of victims at seven, down from an earlier tally of eight.
It added: 'The attacker has been killed'.
The attacker, who was born in 1994, had been killed, it said.
The city lies some 2,100 kilometers northeast of Moscow in the oil-rich Khanty-Mansi region.
"A man was running along the main streets stabbing people", Tass reported, quoting the spokesperson of the local law enforcement.