An aerial view shows an eruption of Mount Aso in Aso, Kumamoto prefecture, southwestern Japan, in this photo taken by Kyodo September 14, 2015. (REUTERS/Kyodo)
Japan on Monday warned tourists to keep away from popular Mount Aso after it began belching smoke and ash into the air, the latest eruption in one of the world's most volcanically active countries.
Authorities issued their third-highest alert and cancelled flights after the huge volcano on the southwestern main island of Kyushu shot a column of ash several thousand metres (a few thousand feet) into the clear sky.
The government said there were no immediate reports of injuries or casualties from the eruption, but the meteorological agency warned any tourists nearby to evacuate quickly.
At least seven domestic flights were cancelled due to the eruption, airlines said.
Mount Aso, a popular tourist spot, has been rumbling into life since last year and in August the meteorological agency also issued an alert after picking up increasing seismic activity around the volcano Sakurajima, south of Aso.
There are scores of active volcanoes in Japan, which sits on the so-called "Ring of Fire", a tectonic zone that records a large proportion of the world's earthquakes.
In June, search teams returned to the peak of Mount Ontake in central Nagano prefecture for the first time in eight months to look for the bodies of six climbers still missing after an eruption that killed dozens.
The shock explosion was Japan's deadliest for almost 90 years, leaving an estimated 63 people dead, many of their bodies at least partially entombed in volcanic sludge.