Tokyo  - Mount Asama in north-central Japan erupted early Monday, spewing volcanic ashes to an altitude of 2,000 metres, the Japan Meteorological Agency said.

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

The mountain erupted at about 1:51 am from the crater, and volcanic smoke was detected until around 8 am.

Mount Asama, on the border between Gunma and Nagano provinces, erupted in August. (dpa)