Russia's Federal Security Service (FSB) said one of its members was killed and five were wounded by an unidentified shooter who opened fire Thursday outside its headquarters in central Moscow.
"One FSB officer was killed in a shootout in central Moscow," the security agency told Russian media, saying that the assailant was acting alone and didn't enter the building.
"An unknown individual opened fire near building No. 12 on Bolshaya Lubyanka Street. There are casualties. The identity of the criminal is being established. The criminal has been neutralized," or killed, the FSB told reporters. The FSB is the main successor agency to the Soviet-era KGB.
The FSB denied earlier reports that the attack had been perpetrated by three assailants. "The perpetrator acted alone," the FSB said.
A spokesman for Russia's Health Ministry was quoted as saying that the five people wounded in the shooting were receiving medical care and that two FSB officers "received very serious wounds."
Crowds could be seen in video posted online fleeing the central Lubyanka Square amid the sound of gunfire.
Kremlin spokesman Dmitry Peskov said President Vladimir Putin was informed about the incident, which came shortly after the Russian leader's annual news conference.
The shooting also occurred on the eve of the Day of Russia's Security Services.
Roughly around the same time that the incident occurred, Putin, a former KGB officer, delivered a speech at a Kremlin concert marking the security services day. He said that at least 54 terror-related crimes had been thwarted in Russia in 2019, including 33 attacks.
The Kremlin-funded RT television channel reported on social media that Russian intelligence services had described Thursday's shooting as "an act of terrorism."
Hours after the incident, the area around the FSB building remained blocked and public transport was rerouted. Numerous law enforcement officers were still present at the scene.
Reuters, The Associated Press, Agence France-Presse, dpa, Interfax and TASS contributed to this report.