A huge blast from an erupting volcano in southwestern Japan shot ash and rocks up to 2,000 metres into the air, with the force of the explosion shattering windows miles away, officials said yesterday.

Authorities widened the danger zone around the 1,421-metre Shinmoedake volcano in the Kirishima range, with its first major eruption for 52 years having sent columns of smoke and ash into the sky since Wednesday.

The volcano’s latest blast came shortly before 8 a.m. (2300 GMT on Monday).

Flying shards from broken hospital windows left a 92-year-old woman with hand and facial injuries, a Kirishima city official told AFP, adding that nearly 200 windows were smashed at schools and public halls.

After the eruption, the Japan Meteorological Agency revised its warning, widening the area at risk from flying debris from three to four kilometres from the peak.

More than 600 residents of the town of Takaharu in Miyazaki prefecture have been forced to evacuate and take shelter in school halls and community centres.

The dome of lava inside the crater, which grows as pressure increases from below, has been expanding quickly amid concerns it could spill over the rim of the volcano and flow down the sides of the mountain.

On Monday, the Japan Meteorological Agency said that the dome was five times larger than it had been on Friday.

It is the volcano’s first major eruption in 52 years, billowing grey smoke into the sky, leading to train and flight cancellations, with television footage showing residents shovelling ash from streets.

A nearby observatory has raised its five-scale warning level on the volcano from two to three, restricting access to the entire mountain.

In April last year the eruption of the Eyjafjoell volcano in Iceland dispersed a vast cloud of ash triggering a huge shutdown of airspace that affected more than 100,000 flights and eight million passengers.