The eruption took place at around 11.43am Tokyo time, the agency said.

There were no immediate reports of casualties or major damage at the popular tourist destination.

But, the meteorological agency raised the alert level for the volcano to Level 3 on a scale of 5, telling people not to approach the mountain.

It also warned of large volcanic blocks and pyroclastic flows scattering within a range of approximately 1km from the mountain’s Nakadake crater.

Ash falls from one of the peaks of the 1,592m mountain in Kumamoto Prefecture will be detected in nearby towns until late afternoon today, according to the agency.

There was a small eruption at Mount Aso in 2019, and 63 people were killed on Mount Ontake in September 2014, which was the worst volcanic disaster in Japan for nearly 90 years.