Residents of a major Chinese city had to turn on the lights at midday Tuesday as exceptionally thick and dark clouds obscured all daylight.

The sky over Hefei, capital of east China's Anhui Province, was reported to be as black as night for 10 minutes during the phenomenon.

Motorists and office workers were forced to turn on their lights until a rainstorm cleared the air.

Wang Dongyong, an expert with the Anhui provincial meteorological station, said the phenomenon was caused by extremely low, thick clouds.

Airport and highway traffic was unaffected.

(Xinhua News Agency April 5, 2006)