A plunging meteor exploded with a blinding flash above central Russia on Friday, setting off a shockwave that shattered windows and hurt over 500 people in an event unprecedented in modern times.
The extraordinary event brought morning traffic to a sudden halt in the Urals city of Chelyabinsk as shocked drivers stopped to watch the falling meteor partially burning up in the lower atmosphere and light up the sky.
It appeared the meteor's entry into the atmosphere was not linked to the asteroid 2012 DA 14 which is expected to pass about 17,200 miles (27,000 kilometres) above the Earth later Friday in an unusually close approach.
But experts said that the fall of such a large meteor estimated as weighing dozens of tonnes was extremely rare while the number of casualties from its burning up around a heavily-inhabited area was unprecedented.
The emergencies ministry said more than 500 people were injured, 112 of whom have been hospitalised. Windows were blown out by the shockwave across the city's region with the ministry saying almost 300 buildings were damaged including, schools, hospitals, a zinc factory and even an ice hockey stadium.
"At 0920 (0320 GMT) an object was observed above Chelyabinsk which flew by at great speed and left a trail behind. Within two minutes there were two bangs," regional emergencies official Yuri Burenko said in a statement.
"The shockwave broke glass in Chelyabinsk and a number of other towns in the region," he said.
The office of the local governor said in a statement that a meteorite had fallen into a lake outside the town of Chebakul in the Chelyabinsk region and television images pointed to a six-metre (20-foot) hole in the frozen lake's ice.
However it has yet to be finally confirmed if meteorite fragments made contact with the Earth and there were no reports that any locals had been hurt directly by a falling piece of meteorite.
Schools were closed for the day and theatre shows cancelled across the region after the shock wave blew out windows amid temperatures as low as minus 18 degrees Celsius (zero degrees Fahrenheit).
The local postal service said several of its buildings had been damaged while some television footage showed people with bloodied faces and at least one child's back covered with blood.
-- 'A large object weighing tonnes' --
The Russian Academy of Sciences said in a statement that it estimated the body to be several metres long and weighing several dozen tonnes. "It burned up at a height of 30-50 kilometres... but pieces could have fallen to Earth as meteorites."
The meteor explosion appears to be one of the most stunning cosmic events above Russia since the 1908 Tunguska Event, when a massive blast most scientists blame on an asteroid or a comet impact ripped through Siberia.
"I am scratching my head to think of anything in recorded history when that number of people have been indirectly injured by an object like this... it's very, very rare to have human casualties," Robert Massey, deputy executive secretary of Britain's Royal Astronomical Society (RAS), told AFP.
But he stressed that he saw "absolutely no connection" between the Chelyabinsk event and asteroid 2012 DA 14, which was to skim the Earth later on Friday at a distance of around 17,200 miles (27,700 kilometres).
With the meteor already becoming a leading trend on Twitter, locals posted amateur footage on YouTube showing men swearing in surprise and fright, and others grinding their cars to a halt.
"First I thought it was a plane falling, but there was no sound from the engine... after a moment a powerful explosion went off," said witness Denis Laskov.
"In a lot of the houses on our street the windows were blown out," he told state television.
Footage is viewable on: http://www.youtube.com/watch?feature=player_embedded&v=_nOaRpF0DJk.
The Chelyabinsk region is Russia's industrial heartland, filled with smoke-chugging factories and other huge facilities that include a nuclear power plant and the massive Mayak atomic waste storage and treatment centre.
A spokesman for Rosatom, the Russian nuclear energy state corporation, said that its operations remained unaffected.
The emergencies ministry said radiation levels in the region also did not change and that 20,000 rescue workers had been dispatched to help the injured and locate those requiring help.