Thousands of villagers have fled to lower ground, causing a mass influx of evacuees in makeshift shelters.
On Friday, soldiers recovered at least 78 bodies from homes and streets, and on Saturday the number of people killed in the inferno rose to 94, as some patients succumbed to their injuries, a hospital official said, bringing the overall toll to 138 since the mountain burst back to life nearly two weeks ago.
The government-delineated "danger zone" has now been expanded to a ring 12 miles from the peak, bringing it to the edge of the ancient royal capital of Yogyakarta.
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.
Many of those people have been evacuated from the danger zone, and now more than 200,000 people are crammed into emergency shelters, including in Yogyakarta.
36,000 are living in the Maguohardjo Stadium in Yogyakarta, which is only designed to cater for 10-thousand.
Outside on the streets, commuters were forced to wear facemasks to protect themselves from inhaling the ash covering the ground.
Scientists can study the patterns of volcanoes, but their eruptions are essentially unpredictable, as Merapi's increasingly intense blasts have shown.