A deadly Indonesian volcano spewing lava and smoke for more than a week erupted on Wednesday with its biggest blast yet, shooting searing ash kilometres into the air as soldiers hastily evacuated villages and emergency shelters.

Women screamed and children cried as they were loaded into trucks while rocks and debris rained from the sky. Several abandoned homes were set ablaze and the carcasses of incinerated cattle littered the scorched slopes.

No new casualties were reported immediately after the booming explosion, which lasted more than an hour.

“This is an extraordinary eruption, triple from the first” on October 26, said Surono, a state volcanologist.

More than 70,000 villagers have been evacuated from the 3,000-metre Mount Merapi's once-fertile slopes since it began erupting just over a week ago, killing 38 people and injuring dozens, most with severe burns.

Almost all have packed into crowded camps well away from the base. — AP