Tokyo  - The volcano Mount Asama in north-central Japan erupted Monday, spewing smoke 2,000 metres above its crater and sending ash as far away as Tokyo, the Japan Meteorological Agency said.

The agency issued a warning of continued large ash deposits in the surrounding 4-kilometre area. No casualties were reported.

The volcano erupted at 1:51 am (1651 GMT Sunday), and volcanic smoke was detected until around 8 am.

A thin layer of ash fell on rooftops and car windows in Tokyo's Tachikawa city, about 100 kilometres south-east of Mount Asama.

The agency said volcanic activity had subsided and the frequency of the volcanic earthquakes had decreased.

The 2,568-metre Mount Asama, on the border between Gunma and Nagano prefectures, last erupted in August.

In southern Japan, several minor volcanic eruptions also had been detected since Sunday on Sakurajima island, south of Kagoshima prefecture, the Fukuoka District Meteorological Observatory said.

The observatory raised the alert level because it said it expected debris could reach surrounding areas within a 2-kilometre radius of the 1,117-metre Sakurajima volcano and volcanic activity might increase. (dpa)