LUMAJANG: The death toll from a sudden, spectacular eruption of Indonesia's Mount Semeru has risen to 13, disaster officials said Sunday, 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 coated in volcanic ash, submerging houses, smothering livestock and leaving at least 900 evacuees seeking cover in mosques, schools and village halls.

Dramatic footage showed Semeru pumping a mushroom of ash into the sky, looming over screaming residents of a nearby village trying to escape.

"The death toll is now 13 people. Rescuers found more bodies," national disaster mitigation agency (BNPB) spokesman Abdul Muhari told AFP.

As many as 10 trapped people were rescued from the surrounding areas in Lumajang, East Java province, Muhari said.

Local broadcaster Kompas TV reported those rescued were local workers at a sand mining site.

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

Lava destroyed at least one bridge in Lumajang and prevented rescuers from immediately accessing the area and those trapped in shelters.

But emergency service footage from one village on Sunday showed a desolate scene, with roofs of houses protruding from the coat of mud that had destroyed them.

The rescue teams were using heavy loaders to remove debris, Muhari said.

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

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

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

Semeru'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.