A meteor crashing in Russia's Ural mountains has injured at least 500 people, as the shockwave blew out windows and rocked buildings.
Most of those hurt suffered minor cuts and bruises but some received head injuries, Russian officials report.
A fireball was seen streaking through the clear morning sky above the city of Yekaterinburg, followed by loud bangs.
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.
"It was quite extraordinary," Chelyabinsk resident Polina Zolotarevskaya told BBC News. "We saw a very bright light and then there was a kind of a track, white and yellow in the sky."
"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.
Among those affected by the meteor were children, in school when it fell at around 09:20 (05:20 GMT).
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 six metres (yards) wide had been found on the shore of the lake.
Asteroid coincidence
The Russian Academy of Sciences estimates that the meteor weighed about 10 tonnes and entered the Earth's atmosphere at a speed of at least 54,000 km/h (33,000mph).
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.
