MOSCOW, August 21. /TASS/. A man died in the ambulance after an explosion in an apartment in northwestern Moscow on Saturday, the city prosecutors’ office said on its Telegram channel.

"The man injured in Malaya Naberezhnaya Street died in the ambulance," the post says.

Earlier, the prosecutors’ office reported that a 14-year-old boy died on the spot and an adult and a 12-year-old boy were injured.

A source with emergencies services told TASS that an unidentified explosive device, possibly an improvised bomb, went off in the apartment. There was no fire after the explosion, nor collapse or damage to the building. Officers of the Russian Investigative Committee have been called to the scene. A police team is working there.