An unidentified gunman opened fire outside the headquarters of Russia’s top security agency in Moscow, killing one officer and wounding five other people.

The Federal Security Service, or FSB, says the assailant was acting alone and didn’t enter the building.

The FSB said the gunman was “neutralised” – a term usually used by Russian officials when an assailant is killed.

The health ministry said five other people were wounded in Thursday’s shooting, including two security officers who were badly injured.

The FSB said the shooting occurred at a building directly behind its headquarters on Lubyanka Square.

Russian police cars block a street next to the FSB security service’s office in Moscow. Photo: Getty

The agency, which is the main successor agency to the Soviet-era KGB, wouldn’t give further details or comment on the attacker’s motives.

In a video shared on social media, loud shots and bangs can be heard.

Vladimir Putin’s spokesman Dmitry Peskov said the president had been informed of the shooting, which came shortly after the Russian leader’s annual news conference.

At about the same time as the gunshots, Putin was making a speech at a Kremlin concert for FSB and other Russian security personnel.

In it he hailed Soviet secret police officers for their efforts in combating terrorism and organised crime, in a speech marking the date the service was founded.