A man walks near temporary shelter at Jumoyo village in the city of Magelang on Thursday as Mount Merapi's volcano erupts. (Beawiharta/Reuters) Indonesia's Mount Merapi was active again just before midnight Friday, killing dozens of people and bringing the death toll since it first erupted last month to 79.

Rescuers said at least 35 people died and 65 were injured, many critically, after a blistering gas cloud ripped through the mountainside village of Bronggang, 15 kilometres from the crater.

Men with ash-covered faces streamed down Mount Merapi on motorcycles, followed by truckloads of women and crying children, after the massive eruption.

Waluyo Raharjo, a search and rescue official, said the bodies from the hard-hit village were being taken to a hospital morgue.

It was not immediately clear why families living within Merapi's danger zone had not already left the area.

Mount Merapi started erupting Oct. 26 and many of the victims died on that day or in the chaotic evacuations.

Three died in an earlier blast on Wednesday, said Eka Saputra, who works at the National Disaster Management Agency.

Scientists — shaking their heads as they watched the wide, fast sweeps of a needle on a seismograph — worried that the worst might be yet to come.

"It looks like we may be entering an even worse stage," said Surono, a state volcanologist, who earlier said continual eruptions since the initial eruption appeared to be easing pressure behind Mount Merapi's magma dome near the tip of the crater. "We have no idea what's happening now."

A mother carries her child as she walks down an ash-covered street in Muntilan as Mount Merapi erupts. (Beawiharta/Reuters)

As rocks and debris rained from the sky late Wednesday, soldiers forced villagers into trucks and carried them down the rumbling mountain. Several abandoned homes were set on fire and dozens of carcasses of incinerated cattle littered the scorched flanks.

Residents in towns up to 240 kilometres away said trees, cars and roads were blanketed in heavy gray ash.

Mount Merapi, which means Fire Mountain, has erupted many times in the last century, often with deadly results.

Still, as with other volcanoes in this seismically charged country, tens of thousands call its fertile slopes home. More than 70,000 are now packed in crowded government camps well away from the base.

Djarot Nugroho, a disaster management agency official, said funds to buy instant noodles, clean water and other supplies for the refugees could run out within days unless the government declared a national disaster, bringing in much-needed federal funds.

There have been more than a dozen strong eruptions at Merapi in the last week and thousands of volcanic tremors and ash bursts, prompting officials to close some air routes above the mountain.

It appeared unlikely, however, that a Qantas plane forced to make an emergency landing after one of its four engines failed while flying over the island of Batam, some 1,400 kilometres away was tied to the smoldering mountain.

The danger zone was widened from 10 to 15 kilometres from the peak, meanwhile, because of the heightened threat.

Indonesia, a vast archipelago of 235 million people, is prone to earthquakes and volcanoes because it sits along the Pacific Ring of Fire, a horseshoe-shaped string of faults that lines the Pacific.

The volcano's Oct. 26 blast occurred less than 24 hours after a towering tsunami slammed into the remote Mentawai islands on the western end of the country, sweeping entire villages to sea and killing at least 428 people.

There, too, thousands of people were displaced, many living in government camps.