(Updates with witness quotes)

TASHKENT, July 10 (Reuters) - A series of explosions at a Soviet-era arms depot in Uzbekistan has killed at least three people and injured many more, witnesses and media said on Thursday.

The blasts in the town of Kagan, near the ancient Silk Road city of Bukhara, destroyed buildings and smashed windows several miles away.

A local witness, who spoke to Reuters anonymously, said the entire city of Kagan, with a population of about 50,000, was cordoned off by troops.

"The sky lit up like at dawn," the witness said, describing explosions that shattered windows in her flat in Bukhara, some 12 km (8 miles) away. The blasts had destroyed Kagan railway station and a five-storey building.

"The city is not accessible... Witnesses say there are many casualties. Hospitals are all full, many are being sent to regional hospitals."

The UzA news agency, which conveys the government line, said in a brief report that the explosions were caused by a fire at a missile and artillery ammunition depot and had killed at least three people and wounded 21.

The site is near a helicopter base used by Soviet forces in the 1980s to support military operations in neighbouring Afghanistan.

The blasts started at 1:48 a.m. (2048 GMT Wednesday) in the tightly run Central Asian nation, where the government controls the press and tolerates little dissent.

The only official statement on the accident was that carried by the UzA agency. It said a special government commission was doing everything to help those injured and to maintain security.

Gas-rich Uzbekistan, where President Islam Karimov has been in power since 1989, is Central Asia's most populous nation. The government is accused by the West of violating human rights. (Editing by Douglas Hamilton)

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