The Sakurajima volcano on Japan's Kyushu island poses a "growing threat", researchers at the University of Bristol say.

The volcano, located 49 km (30 miles) from the Sendai nuclear plant, is also close to Kagoshima, a city of 600,000.

Sakurajima's last deadly eruption was in 1914, when 58 people died.

"The 1914 eruption measured about 1.5km cubed in volume," said the study's lead author Dr James Hickey, who has now joined the University of Exeter's Camborne School of Mines.

"From our data we think it would take around 130 years for the volcano to store the same amount of magma for another eruption of a similar size- meaning we are around 25 years away."