Russia's Federal Security Service (FSB) said on Monday it had thwarted a planned militant attack in Moscow and shot dead an unnamed man it said was plotting a mass shooting in a crowded public place.
State TV channel Rossiya 24 showed a picture of the man, who the FSB said was from a Central Asian country, lying face down dead on the ground with a Kalashnikov assault rifle he had apparently been using nearby.
The FSB said he had opened fire on them when they had tried to arrest him on the outskirts of Moscow and that they had shot him dead.
State TV showed a sports bag nearby containing three hand grenades.
The FSB said the man had links to an international militant group in Syria. The suspect's brother was also detained and a hunt was underway for possible accomplices, it said.
Russia has been the target of attacks by Islamist militant groups in the past, including an attack in 2017 that killed 15 people when an explosion tore through a train carriage in the St. Petersburg metro.
Security officials have said that thousands of people from the former Soviet republics of Central Asia or from the Muslim-majority North Caucasus region of Russia have travelled to Syria or Iraq to fight alongside militant groups.