A mysterious bright flash turned night into day over a huge area of Russia - sparking fears the US had launched a strike on North Korea.

The explosion of light accompanied by the 'ground shaking' was also blamed on a UFO visitation or a meteor exploding in the atmosphere.

The phenomenon was seen and felt over thousands of miles in Russia, but was especially evident in three regions Bashkortostan, Udmurtia, and Tatarstan.

Russian officials and scientists immediately denied that there had been a Russian missile test or any reported space rock crashing to earth.

A mysterious bright flash turned night into day over a huge area of Russia, prompting fears the US had launched a strike on North Korea. This was the scene in the region of Tatarstan as the sky turned blue in the middle of the night

The explosion of light accompanied by the 'ground shaking' was also blamed on a UFO visitation or a meteor exploding in the atmosphere. Pictured: The sky over Tatarstan during the mysterious explosion of light

Videos show how for a few moments the dark night sky - just after midnight in the Urals - was lit up, turning a vivid blue as if on a bright summer's day.

'It lit the night sky from side to side, making it look brighter than daylight,' said one account.

'We saw this while driving - there was a vibration and the sound of explosion in the sky, awesome,' said Artyom Russkikh, a reported by The Siberian Times, which collected witness statements of the flash on the night following Russian Orthodox Christmas Day this week.

He asked: 'What was it? A meteor, a rocket from space, UFO, North Korea?'

Firaya Zaripova commented on the light show in the early hours of Monday morning: 'Probably it was the testing of some military weapon, if even the ground was shaking.'

But there were denials Vladimir Putin had ordered any military tests that could have produced this dramatic scene.

Videos show how for a few moments the dark night sky - just after midnight in the Urals - was lit up, turning a vivid blue as if on a bright summer's day

There were denials Vladimir Putin had ordered any military tests that could have produced this dramatic scene

Ilnaz Shaykhraziev said: 'I saw the flash in Menzelinsk. There was also the sound of an explosion and then a vibration, I felt it.'

Another witness Denis Rozenfeld said: 'A meteor burned out, not reaching the lower layers of the atmosphere.

'Before this it exploded and split into many small pieces. That is why there was such a sound, which came to us in a few seconds.

'It's a funny coincidence that such a rare phenomenon for our region has happened right over Christmas.'

Reports of similar flashes have occurred three times in 12 years in Russia. Yet experts were split on the cause of the flash.

Reports of similar flashes have occurred three times in 12 years in Russia. Yet experts were split on the cause of the flash

Astronomers from Kazan Federal University in Tatarstan insisted there was a space link

Yuri Nefefyev, director of the Engelhardt Astronomical Observatory, claimed atmospheric electricity was behind the eerie night-to-day explosion of light.

'There are a huge number of effects linked to atmospheric electricity, many of which are not properly studied because of how rarely they occur,' he said.

Astronomers from Kazan Federal University in Tatarstan insisted there was a space link.

'This was a bolide, when all substance burns in atmosphere and doesn't reach Earth,' said Dr Sergey Golovkin, of the university's Physics Institute.

'It is accompanied by a loud bang. It could have been a fragment of a spacecraft that burnt, but normally it takes them more time to enter the atmosphere, thus they can be observed for longer.

'This was a bolide that burnt in the dense layers of the atmosphere which is why it was seen over such a big territory.

'We didn't register the flash because there was strong blizzard on this night.'