The eruption of Aso volcano, which is considered one of the largest in Japan, occurred in the southwestern prefecture of Kumamoto on the island of Kyushu, TASS reported quoting the National Meteorological Administration of the country, NHK reported.
Smoke mixed with volcanic ash rose about 200 meters from the mountain's crater.
The agency raised the alert level for Mount Aso to two on a scale of one to five on Sunday, after detecting active volcanic tremors and an increase in volcanic gas emissions.
People within roughly one kilometer of the crater are being urged to stay alert for huge airborne volcanic rocks and pyroclastic flows.
Aso is one of the largest volcanoes in the world. Its height is 1,592 m.