TOKYO, April 19 (Xinhua) -- Mt. Aso in the southwestern Japanese prefecture of Kumamoto erupted on Friday, the weather agency here said.

The eruption occurred at 8:24 a.m. local time (2324 GMT Thursday), the Japan Meteorological Agency (JMA) said.

The agency said the eruption occurred at the volcano's No. 1 Nakadake crater and maintained its warning level at 2 on its scale which peaks at 5, warning people not to approach the crater of the volcano.

The warning was upgraded following a small eruption observed earlier this week, the JMA said, adding that Friday's eruption saw smoke and ash spew as high as 400 meters in the air.