Flights in Japan were cancelled or diverted on Thursday to avoid a cloud of ash and smoke spewing from an erupting volcano in the south.

Japan Airlines and All Nippon Airways warned passengers of "a number of cancellations and changed destinations" on routes involving Kumamoto airport because of the 800-metre (2,600-foot) column of debris from Mount Aso.

"Today we cancelled eight flights departing from Kumamoto and four flights arriving there," a JAL spokesman said.

"There was also one flight which changed destination" to a nearby airport," he said, adding that more could be affected if the eruption worsens.

A spokesman for the airport said one international flight had been cancelled and one diverted.

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.

kh/hg/cah/mtp

Japan Airlines

All Nippon Airways