A Japanese soldier was killed on Tuesday after a volcano erupted near a popular Japanese ski resort, sparking an avalanche that left several injured and scores stranded up a mountain, officials said.

Footage broadcast on Japanese television showed thick black smoke interspersed with falling rocks rolling down the snow-covered side of the volcano towards a ski slope.

“One of the six members of the Self Defence Forces (injured in the incident) has died after being caught up in an avalanche,” a defence ministry spokesman told AFP.

The ministry had earlier said that six infantry personnel who had been on a training mission on Mt. Kusatsu Shirane, northwest of Tokyo, were hit by the avalanche but had been rescued.

The falling rocks kicked clouds of snow into the air as they made impact.

“Black smoke rose from the top of the mountain and we were told to evacuate inside 30 minutes later,” a man who was at the ski resort told public broadcaster NHK.

“About 100 people have been evacuated,” he said.

A local town official said that a total of 78 people, some of them suffering injuries, were stranded at a gondola station at the top of the mountain. The gondola has been stopped because of a power outage.

“We're now discussing how we can evacuate them,” the official said.

NHK said eight of those stranded had already been rescued. Television footage showed military helicopters buzzing overhead as people were airlifted to safety.

A woman who was stranded at the ropeway station but later rescued told Japanese TV: “There was an eruption in front of my eyes. Black and white plumes came towards me. Then the ski slope went completely black.”

A snowboarder told NHK his gondola had stopped suddenly and he saw that other gondolas around him had broken windows and were covered in ash.

“I realised it was an eruption. Forty to 50 minutes later, all the gondolas moved up to the station on the top of the mountain,” he said.

The area had seen heavy snowfall in the hours leading up to the eruption, making the slopes ripe for avalanches.

"Ring of fire"

Japan's Meteorological Agency urged people to stay away after it detected what it said was “slight volcanic activity.”

“Today an eruption occurred” at the volcano, agency official Makoto Saito told reporters.

He warned that the volcano could still spew more rocks and ash, and that there was a risk of further avalanches.

A local fire department official told AFP that 10 people had been injured in the incident.

“Five of them were seriously injured. We began sending the injured to a hospital,” he said.

Among the injured were four people hurt by shattered glass while on a ropeway gondola at the ski resort in Gunma.

The official said an earlier report that one person was missing in the avalanche was not accurate.

Japan, with scores of active volcanoes, sits on the so-called Pacific “Ring of Fire” where a large proportion of the world's quakes and volcanic eruptions are recorded.

On September 27, 2014, Japan suffered its deadliest eruption in almost 90 years when Mount Ontake, in central Nagano prefecture, burst unexpectedly to life.

An estimated 63 people were killed in the shock eruption, which occurred as the peak was packed with hikers out to see the region's spectacular autumn colours.

According to the Meteorological Agency, this was the first time this volcano has erupted since 1983. There are currently 111 active volcanos, according to agency officials.