A meteor crashing in
Russia's Ural mountains has injured at least 500 people, as the
shockwave blew out windows and rocked buildings.
A fireball was seen streaking through the clear morning sky above the city of Yekaterinburg, followed by loud bangs.
President Vladimir Putin said he thanked God no big fragments had fallen in populated areas.
A large meteor fragment landed in a lake near Chebarkul, a town in the neighbouring Chelyabinsk region.
Much of the impact was felt in the city of Chelyabinsk, some 200km (125 miles) south of Yekaterinburg.
"The explosion was so strong that some windows in our building and in the buildings that are across the road and in the city in general, the windows broke."
Officials say a large meteor partially burned up in the lower atmosphere, resulting in fragments falling earthwards.
Thousands of rescue workers have been dispatched to the area to provide help to the injured, the emergencies ministry said.
The Chelyabinsk region, about 1,500km (930 miles) east of Moscow, is home to many factories, a nuclear power plant and the Mayak atomic waste storage and treatment centre.
'Blinding'
Of 514 people injured in the Chelyabinsk region, 11 were being treated in hospital, the regional emergencies agency said in a statement.
Mr Putin promised "immediate" aid for people
affected, saying kindergartens and schools had been damaged, and work
disrupted at industrial enterprises.
Video posted online showed frightened, screaming youngsters at one Chelyabinsk school, where corridors were littered with broken glass.
Chelyabinsk resident Sergei Serskov told BBC News the city had felt like a "war zone" for 20 to 30 minutes.
"I was in the office when suddenly I saw a really bright flash in the window in front of me," he said.
"Then I smelt fumes. I looked out the window and saw a huge line of smoke, like you get from a plane but many times bigger."
"A few minutes later the window suddenly came open and there was a huge explosion, followed by lots of little explosions."
In Yekaterinburg, 36-year-old resident Viktor Prokofiev was driving to work when he witnessed the event.
"It was quite dark, but it suddenly became as bright as if it was day," he was quoted by Reuters as saying.
"I felt like I was blinded by headlights."
Debris also reportedly fell on the west Siberian region of Tyumen.
The governor of Chelyabinsk region, Mikhail Yurevich, reported that the meteor had landed in a lake 1km outside Chebarkul, which has a population of 46,000.
A Russian army spokesman said a crater 6m (20ft) wide had been found on the shore of the lake.
Asteroid coincidence
It would have shattered about 30-50km (18-32 miles) above ground, with most of the meteor burning up.
Scientists have played down suggestions that there is any link between the event in the Urals and 2012 DA14, an asteroid expected to race past the Earth on Friday at a distance of just 27,700km (17,200 miles) - the closest ever predicted for an object of that size.
Prof Alan Fitzsimmons, of the Astrophysics Research Centre at Queen's University Belfast, said there was "almost definitely" no connection.
"One reason is that 2012 DA14 is approaching Earth from the south, and this object hit in the northern hemisphere," he told BBC News.
"This is literally a cosmic coincidence, although a spectacular one."
Such meteor strikes are rare in Russia but one is thought to have devastated an area of more than 2,000 sq km (1,250m) in Siberia in 1908.
Asteroids, meteors and meteorites
- Asteroids are small bodies that orbit the Sun as the Earth does
- Larger asteroids are called planetoids or minor planets, smaller ones often called meteoroids
- Once any of these enters our planet's atmosphere, it becomes a meteor
- Many meteors break into pieces or burn up entirely as they speed through the atmosphere
- Once meteors or fragments actually impact the surface, they become meteorites
