Japan's snow-capped Mount Usu volcano erupted yesterday and early today, belching vast clouds of smoke and ash and forcing 15,000 people to flee their homes.
The 732-metre volcano, among Japan's most active, sent rocks hurtling into the air as plumes of dark grey smoke streaked with blue lightning billowed from the conical mountain. Residents ran for cover, holding towels over their mouths as the smell of sulphur pervaded the air.
Onlookers said they could taste grit from the eruption that hurled ash as high as 2,700 metres into the sky. A carpet of ash coated cars and houses.
Government officials said the latest eruption would likely continue and one expert who viewed the site by helicopter said the worst may be yet to come.
"It is our common opinion that the main magma [molten rock] has yet to surface," Prof Hiromu Okada told a news conference.
The area was also shaken by an earthquake overnight, the latest in a series to hit the area over the past few days, apparently the result of the volcanic activity.
Tremors were jolting the hot spring resort area on the northern island of Hokkaido as the eruption continued, Mr Manabu Komiya, an official of the Meteorological Agency, said.
Ash, volcanic rocks and mudslides had flowed towards the small town of Abuta and the navy and the Coast Guard were deployed to evacuate the entire population of some 2,000 from homes perched precariously between the mountain and the sea.
Officials said four naval ships, five Coast Guard vessels and two military helicopters had plucked residents to safety.
"Depending on developments, the eruption could cause even bigger damage," the Prime Minister, Mr Keizo Obuchi, said. "The government will do whatever it can to deal with the situation."
Sailors on naval vessels reported mudslides slipping down the cone-shaped mountain towards Abuta, but navy officials said later these were small.
Officials said there were no reports of casualties.
Mount Usu last erupted in 1978 after a series of earthquakes that gave birth to a new and smaller volcano by its side. Mudslides triggered by that eruption killed three people.
Troops had already helped to evacuate more than 15,000 people from towns around the foot of the volcano and they were being housed in schools and public halls.
Officials said they were establishing emergency post offices and banks to allow residents easy access to their money.
Government experts said another big explosion appeared unlikely but it could take some time until the volcano settled down and more eruptions were possible from new craters.
"The fact that the ash cloud rose so high suggests the force of the eruption was strong. We can't dismiss the chance of other developments, like magma moves", said Mr Yoshiaki Ida, chairman of the government's volcano experts panel.
Officials said initial assessments showed the initial eruption had not been as large as first expected.