Dozens of hikers were stranded Saturday on the slopes of an erupting Japanese volcano that has reportedly killed one person and left 30 more seriously injured.

Dozens of hikers were stranded Saturday on the slopes of an erupting Japanese volcano that has reportedly killed one person and left 30 more seriously injured.

Ash, rocks and steam continued to spew from Mount Ontake more than nine hours after it sprang violently to life as around 250 people were trying to scale its peak.

Four people were buried by the ash, with one having been dug out, Kyodo News reported.

"I first thought it was thunder as I heard a bang and another bang, two or three times," a trekker told public broadcaster NHK. "Then volcanic dust fell noisily."

Amateur cameraman Keiji Aoki told Jiji Press: "It was tremendous. I prepared for death when I got caught in the dust under a pine tree."

A suffocating blanket of ash up to 20 centimetres (8 inches) deep covered a large area of the 3,067 metre (10,121-foot) volcano, trapping climbers and forcing up to 150 into mountaintop shelters at one point.

Around 230 people have now reached the bottom but a further 40 are trapped at the summit where they will spend the night in shelters, local media reported.

Aerial footage of Mt. Ontake showed several cabins smothered with the thick dust, some with windows that appear to have been shattered by the force of the eruption.

NHK said 32 people had been seriously injured, including more than 10 who were unconscious. The broadcaster said one woman was now known to have died.