Japan's Mount Asama volcano has erupted, spewing smoke almost 2km (1.3 miles) into the air and causing ash to drift over parts of the capital, Tokyo.There were no reports of injuries or damage in the sparsely populated area around the mountain, 145km north-west of Tokyo.
Chunks of rock from the explosion were found about 1km from the volcano.
Residents living within a 4km radius of the mountain have been urged to be cautious.
Volcanic ash fell on nearby areas as well as parts of Tokyo, Japan's meteorological agency said.
TV reports showed neighbourhoods sprinkled with white flakes.
Mount Asama is 2,568m (8,425 ft) high, with snow-covered peaks. No lava flows could be seen.
Video: Volcano Erupts