One officer of the Federal Security Service (FSB) was killed during the shooting in central Moscow, a spokesperson with the FSB said.
Earlier, the FSB said that a suspected gunman who opened fire in central Moscow had been eliminated, and his identity was still to be determined.
"An unknown gunman opened fire in Bolshaya Lubyanka Street, 12. There are injured as a result of the incident. The gunman has been eliminated, his identity is being determined," the statement by the FSB says.
According to the Russian Investigative Committee, a criminal case has been opened into an attempt to kill law enforcement agents.
Two FSB officers were seriously injured during the shootout, a spokesperson for the Russian Healthcare Ministry told the media.
Russia's President Vladimir Putin is being updated on the shooting incident in central Moscow, presidential spokesman Dmitry Peskov said.
A shootout took place near the Federal Security Service (FSB) headquarters in central Moscow on Thursday.
The FSB has refuted media reports that claimed there were three attackers.
"There was one attacker...And he did not enter the FSB building," a spokesperson with the FSB PR department said.
Earlier, an eyewitness who was near the shooting scene shared his experience:
"Around 6 pm a loud bang was heard, followed by gunfire. The gunshots have stopped by now."