Mount Semeru in eastern Java, about 310 kilometres west of the tourist hotspot of Bali, erupted at 2:13 pm local time (0713 GMT), spewing what are known as pyroclastic flows, Indonesian geological agency head Muhammad Wafid said.

"The public is advised not to engage in activities within an 8 kilometre (5 mile) radius of the crater or peak of Mount Semeru due to the risk of being struck by ejected rocks," he said in a statement.

The local disaster agency said the plume of ash had risen as far as 8.5 kilometres into the air, although Wafid said thick fog blanketing the mountain had made measurements difficult.

The geological agency also said that seismic activity at Mount Semeru remained high.

There have been no immediate reports of evacuations or casualties caused by the eruption.

Authorities at Ngurah Rai airport in Bali said flight schedules were operating as usual so far.

An eruption by Semeru in 2021 killed more than 50 people and damaged more than 5,000 homes, forcing almost 10,000 people to seek refuge.

Indonesia sits on the Pacific "Ring of Fire", where the meeting of continental plates causes substantial volcanic and seismic activity.

The Southeast Asian archipelago has nearly 130 active volcanoes.