MOUNT MERAPI - THE tiny hospital at the foot of Mount Merapi struggled on Saturday to cope with victims brought in after the fiery volcano unleashed its most powerful eruption in a century - some with burns covering 95 per cent of their body.

The only sign of life in one man, who's eyes were milky gray in colour and never blinked, was the shallow rising and falling of his chest. Others, their lungs choked with abrasive volcanic ash, struggled to breathe.

Indonesia's most volatile mountain unleashed a surge of searing gas, rocks and debris on Friday that raced down its slopes at highway speeds, torching houses and trees and incinerating villagers caught in its path.

With more than 90 killed, many of them after succumbing to their injuries, it was Merapi's deadliest day in decades, but Sigit Priohutomo, who works at Sardjito hospital, predicted the toll would rise.

With nearby airports closed because of poor visibility, ventilators needed for burn victims were stuck in the capital, Jakarta, he said. In meantime, nursing students were using emergency respirators pumped by hand.

The volcano, in the heart of densely populated Java island, has erupted many times in the last two centuries, but many people choose to live on its rolling slopes, drawn to soil made fertile by molten lava and volcanic debris.

Merapi death toll hits 138