Tokyo (AFP) - 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.
- Troops sent to rescue hikers -
The eruption came on a busy autumn day on a mountain popular among hikers at this time of year.
Footage apparently filmed by someone on the volcano as it erupted showed towering columns of thick smoke surging into the air and then cascading down its flanks, enveloping walkers.
"The speed of the smoke was too fast. You can't escape," a climber told NHK. "I'm worried that many more people are still on the mountain."
Another climber told how it became impossible to breathe and said rocks were falling "like hailstones".
In Tokyo, Prime Minister Shinzo Abe ordered the military to send troops to the peak to rescue hikers.
"We have confirmed that there have been injuries," Abe told reporters. "I ordered (government officials) to do their best to secure the safety of mountain climbers."
Earlier in the day, local authorities said they had received reports from people on the mountain that at least 11 hikers had been injured, including seven unconscious.
"We are trying to confirm the reports," said Sohei Hanamura, an official of the Nagano prefectural government.
"We have not received any reports of death but we are afraid that the number of casualties would increase," Hanamura told AFP by phone.
NHK said three people were trapped outside by the ash and rocks falling around them.
"There was a thunder-like noise and the sky became dark because of the smoke," Shuichi Mukai, who runs a mountain lodge near the summit, told Kyodo News.
Climbers who fled the eruption spoke of their relief.
"I escaped with my life," a local resident told NHK. "Immediately after I saw the eruption, I rushed away but I was soon covered with ash."
Another male climber told how he had cowered behind a rock during the worst of the eruption.
"No one could escape while the smoke was so intense," he said.
The meteorological agency forecast further eruptions, warning that volcanic debris may settle within four kilometres (2.5 miles) of the peak.
The agency also placed restrictions on access to the mountain, while calling on local residents to remain on alert as an eruption could shatter windows miles away.
The last significant eruption of Mount Ontake, which straddles Nagano and Gifu prefectures in the centre of the country, was in 1979 when it expelled more than 200,000 tonnes of ash, according to local media.