At least one person has been killed in a shooting in downtown Moscow on Thursday evening, state media have reported.
An unidentified gunman opened fire near the entrance of the Federal Security Services (FSB) building before being killed in a shootout, RIA cited an FSB spokesperson as saying.
One FSB officer was killed at the scene, the FSB was cited as saying.
The Health Ministry said in a statement that five people had been injured, while earlier media reports said that two FSB officers were critically injured.
A video of the incident depicted people fleeing the scene with gunfire heard in the background.
The Moskva news agency reported that three shooters had stormed the FSB building in the attack, two of whom were killed in the initial shootout. The agency said that the third shooter escaped down the street and had been surrounded and killed by security forces.
The news agency later took down the article and the FSB denied reports that there had been three shooters.
The FSB was later cited as saying that there had only been one shooter — and that he had not managed to enter the building before being killed.
The shooting took place on the eve of Russia's Day of Security Forces, celebrated Dec. 20. President Vladimir Putin was attending a concert on Thursday evening dedicated to the holiday at the Grand Kremlin Palace, hours after his annual press conference.
A source close to the FSB told Reuters that the shooting may have been planned to coincide with the celebrations.