A huge volcano in southern Japan was belching smoke and ash 1,000 metres (3,000 feet) into the air Wednesday, the latest eruption in one of the world's most volcanically-active countries.

Mount Aso, whose huge caldera dominates the southwestern main island of Kyushu, rumbled into life on Tuesday.

Meteorologists warned volcanic stones and ash could fall in a one-kilometre (half a mile) radius of the volcano.

The eruption is Aso's first in 19 years and comes two months after Mount Ontake in central Nagano killed more than 60 hikers when it erupted without warning.

Last month, experts warned a disaster on Kyushu island, which has been struck by seven massive eruptions over the past 120,000 years, could see an area that is home to seven million people buried by molten rock in just two hours.