Indonesia's Mount Merapi volcano spewed heat clouds and ash on Monday as officials warned another eruption is expected, though possibly not as big as one that killed 34 people last week.

Searing grey fumes and ash shot high into the sky and rolled down the slopes of the 2,914-metre (9,616-foot) mountain, Indonesia's most active volcano, spreading fear and panic among nearby residents in central Java.

Merapi, a sacred landmark in Javanese culture whose name translates as "Mountain of Fire", has convulsed regularly since last Tuesday's major eruptions, driving up to 50,000 people into temporary shelters.

"There'll be more eruptions as not all the energy has been released. Eruptions will continue to take place in the weeks ahead," volcanologist Surono said.

He said there was no current need to expand a 10-kilometre (six-mile) exclusion zone around the mountain, but warned those in cramped shelters it was still too unsafe to go back to their homes.