A MASSIVE mushroom cloud erupted near Moscow after a suspected drone attack on a tech plant where Putin's stealth bombers are reportedly stashed.
At least one person was killed in the explosion at the Zagorski plant that sent flames and smoke billowing hundreds of feet into the sky.
The blast close to Russia's capital, which has left at least six people missing, blew out windows in nearby apartments.
Natalia Nikitina, 45, died in hospital after suffering horrific burns when the plant in Sergiyev Posad erupted.
A driver for the company that rented the building, Piro-Ross, remains missing under the rubble.
The plant is closely involved in the development of Russia’s new generation stealth bomber, independent Russian media outlet Agentstvo reported.
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Russia's government public procurement website indicates the firm supplies optics to Putin's security forces.
It seems that the company have been articipating in the development of the tyrant's new-generation strategic missile-carrying bomber, a project known as Messenger, since 2019.
The report said: "State contracts of the plant ceased to be published almost immediately after the start of the war - from March 2022.
"But the contracts concluded earlier are still available.
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"Among them - ‘implementation of an integral part of the development work on the topic code: Messenger-1OEP / L'.
"The term of the contract is 2027, the cost of the work is 69 million roubles” - £560,000 at current prices after a collapse in the value of Russian currency caused by Putin's war."
Extraordinary pictures show the towering pillar of smoke and fire after the mega blast at the plant in Sergiyev Posad.
Witnesses reported a "whistle, flash and a roar" as the blast rocked the factory in Moscow region.
Early reports that pinned the explosion on a drone attack were later denied by Russian officials - but people in the area reported seeing something flying towards the building.
However, local officials instead blamed the explosion on an industrial accident at the plant.
At least 49 people are reported to have been injured and witnesses said the plant - used to make optics for missiles, jets, night vision goggles and rifle scopes - is "in ruins".
Six people are in a serious condition, Mash media reported.
And it's feared up to five people may be buried under the rubble, Moscow region governor Andrey Vorobyov said.
It's understood the blast happened in a warehouse containing pyrotechnic equipment.
Deaths are feared as first responders are desperately digging beneath the rubble.
Pictures showed nearby streets strewn with debris hurled out from the enormous blast.
And locals reported being thrown backwards by the force of the explosion.
The exact cause of the explosion has not been officially confirmed - but it came after Russia was once again menaced by Ukrainian kamikaze drones last night, with two reportedly shot down overnight in nearby Moscow.
Witnesses have reported a truck exploding at the site - which also produces explosives and pyrotechnics used by Russia.
Others said they had heard a strange "whistling" sound before the enormous blast rocked the town.
Windows have been blown out from nearby houses and an evacuation has been issued as the 17,000-square-foot site continues to burn.
Another local report said the whole town was ordered to evacuate.
Sabotage attacks along with mysterious explosions and fires have been reported across Russia since Vladimir Putin's vile invasion of Ukraine last February.
A worker at the plant suggested it was attacked by a drone.
“Something flew in,” the anonymous source told VChK-OGPU Telegram channel.
“First a whistle, then the light blinked and an explosion. There was 'a vacuum, a flash and a roar'.
“They had magnesium and gunpowder there.”
Another witness said: "It’s terrible, the whole plant is destroyed. I'm shocked.
“Imagine, we were just thrown back [by the blast] in the welding section. It's just awful.”
Two shells were found among the debris - but it is unclear if they were linked to the explosion.
The main plant produces night sights for Russian tanks and other hi-tech military items.
But explosives were on part of the territory leased to PiroRos company, which also had dealings with the defence Ministry.
Baza media said that state investigators were examining “sabotage” as a possible cause of the giant blast.
The plant itself is one of the main developers and manufacturers of a wide range of observation devices, medical equipment for diagnosing and treating diseases of eye tissues and vessels, fluorographs and X-ray image intensifiers, as well as various photometric devices.
It is a leading enterprise for the development and serial production of binoculars and monoculars, and is believed to have links to the defence ministry in Russia.
Russian official Sergei Pakhomov said: “The source of the detonation was a pyrotechnics warehouse, the premises for which were rented by one of the well-known companies in the city.
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“The cause of the explosion is in violation of technological processes.”
Baza reported that the director of the Piro-Ross denied an explosion in his pyrotechnic warehouse.