A small volcanic eruption at a valley on Mount Hakone in Japan forced officials to close part of the Hakone Resort and Spa near Tokyo during one of the peak tourist seasons.

Japan’s Meteorological Agency has raised the warning level on the mountain to 3 from 2, for the Oowakudani Park in Hakone town. According to an agency official, the alert of the area, covering 80 km west of Tokyo has increased "to a new level".

Route 734 and 735 (Souunzan through Ubako) have been shut down, and buses that run through the area have been pulled out.

"If hot water or magma becomes involved, it could explode at a deeper level, and there would probably be very little warning."

Hakone resort and spa is a Hyatt Regency hotel, featuring guest rooms which span a minimum of 56m2 and provides an elaborate view of the mountains.

It also features six dog-friendly rooms, and a dining room restaurant specialising in French cuisine and sushi. It has a spa (IZUMI), two meeting rooms that can accommodate up to 30 people, and two natural hot springs, which are one of the main attractions.

Reuters cited volcanologist Toshitsugu Fujii as saying: "If hot water or magma becomes involved, it could explode at a deeper level, and there would probably be very little warning".

"Things are now taking place at a shallow level and probably it won’t go that far. But you can’t say when that might change."

Japan is one of the world’s most seismically active nations. In September last year, 63 people died after the sudden eruption of a peak volcano.