At least eight people died in a fire in an office building near Moscow, including two who jumped from the building to escape the flames, authorities said.
State news agency Tass said the fire in Fryazino, about 15 miles north east of the Russian capital, was caused by a malfunctioning electrical system.
Videos shared on social media show thick plumes of smoke rising from windows throughout the multistory office building.
The regional governor Andrei Vorobyev said in a post on the social platform Telegram that oxygen tanks stored in the building exploded, causing some ceilings to collapse.
Two people died when they jumped from the building and six more died inside, Mr Vorobyev said.
He said offices in the building were rented by 30 different companies, including the Platan Research Institute, which produces electronics.
The Platan Research Institute is among several Russian companies sanctioned by the US Treasury for meddling in foreign elections, carrying out malicious cyber operations and undermining security abroad.
The Treasury listing said the Platan Research Institute is based at the same address as the building that caught fire.
The website for the town of Fryazino - which touts itself as a centre of scientific excellence - said the Platan Research Institute is the "leader, sole developer and manufacturer", in Russia of a number of "unique devices," including lasers, flat liquid crystal screens, video modules and white-emitting LED lighting.
Russian newspaper Kommersant was more descriptive, saying the Institute develops equipment used by Russia's military, including in fighter jets, bombers and helicopters, as well as in missiles, "all types of nuclear submarine missile carriers," long-range radar and anti-aircraft missile systems.
Kommersant said the company was created to develop electron beam devices for radar and space technology, mainly for defence purposes.
Ruselectronics, the Platan Research Institute's parent company, denied that the company was affected by Monday's blaze. In a statement published by Tass, state-owned Ruselectronics insisted the building had passed to private ownership in the 1990s and that the Institute was no longer a tenant.
Independent Russian media suggested the company had recently moved to a neighbouring building.
