The death toll from a sudden, spectacular eruption of Indonesia's Mount Semeru has risen to 14, disaster officials said, as rescuers searched villages blanketed in molten ash for survivors.

The eruption of Java's biggest mountain caught locals by surprise on Saturday, sending thousands fleeing its path of destruction and forcing hundreds of families into makeshift shelters.

It left at least 11 villages of Lumajang district in East Java province coated in volcanic ash, submerging houses and vehicles, smothering livestock and leaving at least 900 evacuees seeking shelter in mosques, schools and village halls.

Dramatic footage showed Semeru pumping a mushroom of ash into the sky, looming ominously over screaming residents of a nearby village as they fled.

At least 57 people were injured in the eruption, of whom 41 suffered burns and were hospitalised, the BNPB said in a press release.

Evacuations were temporarily suspended today due to hot ash clouds, Indonesia's Metro TV reported.

There is also a risk of heavy rain causing ash sediment to form a new river of hot lava, the country's top volcanologist told the station.

Lava mixed with debris and heavy rain had already destroyed at least one bridge in Lumajang, preventing rescuers from immediately accessing the area.

Rescue workers dressed in bright orange uniforms worked against a dark-grey backdrop, a scene of ruin surrounded by buckled buildings and fallen trees.

In others, villagers tried to salvage their belongings from wrecked homes. Some held mattresses and furniture on their shoulders while others carried goats alive in their arms.

The rescue teams were using heavy loaders to remove debris and clear roads.

Locals have been advised to not travel within 5km of Semeru's crater, and the air around it is highly polluted and could affect vulnerable groups.

Officials have sent aid to shelters, including food, tarpaulins, face masks, and body bags.

Ash spewed by the volcano travelled up to 4km from the volcano, Indonesia's geological agency said, reaching as far as the Indian Ocean in the southern part of Java island.

But Australia's Volcanic Ash Advisory Centre, which provides advice to the aviation industry, said the ash had now dissipated around Semeru, according to satellite imagery.

The volcano's alert status has remained at its second-highest level since its previous major eruption in December 2020, which also forced thousands to flee and left villages covered.

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

The Southeast Asian archipelago nation has nearly 130 active volcanoes.

In late 2018, a volcano in the strait between Java and Sumatra islands erupted, causing an underwater landslide and tsunami which killed more than 400 people.