On the other side of the archipelago, storms again prevented aid deliveries to increasingly desperate survivors of a tsunami — including a teenage girl with an open chest wound — that killed 413 people in the Mentawai islands. Relief workers found some comfort, however, when the number of missing dropped by half to 163 as searchers discovered more survivors and villagers who had fled to the hills returned home.

The simultaneous catastrophes have severely tested the emergency response network. Indonesia lies in the Pacific "Ring of Fire," a cluster of fault lines prone to earthquakes and volcanic activity.

Mount Merapi, which sprang back to life early this week, unleashed a terrifying 21-minute eruption early Saturday, followed by more than 350 volcanic tremors and 33 ash bursts, said Surono, chief of the Center for Volcanology and Geological Hazard Mitigation.

The latest spewing of the notoriously unpredictable volcano forced the temporary closure of an airport and claimed another life, bringing the death toll this week to 36.

At least 47,000 people have fled the mountain’s wrath, according to the National Disaster Management Agency. Government camps well away from the base were overflowing with refugees, including most of the 11,000 people who live on the mountain’s fertile slopes. They were told Saturday, with signs the danger level was climbing, that they should expect to stay for three more weeks.

Despite such warnings, many people have returned to their land to check on precious crops and livestock. The new eruption triggered a chaotic pre-dawn exit, killing a 44-year-old woman who was fleeing by motorcycle, said Rusdiyanto, head of disaster management office in the main city of Yogyakarta.

For the first time Saturday, more than 2,000 troops were called in to help keep villagers clear of the mountain. Camouflaged soldiers stood guard in front of ash-covered homes and local television showed one woman who refused evacuation orders being carried away as she screamed in protest.

Still, the villagers may be later allowed to go back for a few hours a day if the volcano appears to be calm, said Djarot Nugroho, head of the Central Java disaster management agency, adding that they must return to the camps immediately if a new alarm is raised.

"Once the sirens go off, no excuse, everyone has to get back to the camps," he said.

The eruption temporarily forced the closure of the airport in Yogyakarta, 12 miles (20 kilometers) south of the volcano, because of poor visibility and heavy ash on the south of the runway, said Naelendra, an airport official.

Despite earlier hopes that Merapi’s activity might be waning, scientists warned Saturday the worst may be yet to come.

High-pressure gas appeared to be building up behind a newly formed thick magna dome in the crater, "setting the stage, potentially, for a more explosive eruption," said Subandrio, who heads the nearby volcanology center.

"It’s a bad sign," he said.

In the tsunami zone, where more than 23,000 people have been displaced, government agencies were forced to pull back boats and helicopters that had been ferrying noodles, sardines and sleeping mats to the most distant corners of the Mentawai islands because of stormy weather and rough seas.

The death toll climbed to 413 Saturday, but officials halved the number of missing people after a total of 135 people were found by searchers or returned home after fleeing to the hills. Volunteer searcher Patigor Siahaan said three children — aged 6, 7 and 8 — were discovered in the rubble of their collapsed house, where their parents died. Most of the others were found in small groups.

Rescue workers had hoped to airdrop aid using a plane and four helicopters Saturday, but storms made it too dangerous, said Ade Edward, an official with the provincial disaster management agency.

He said navy ships on their way to the devastated area had been halted by 18-foot (six-meter) waves and were stranded in the port of Padang on Sumatra, one of Indonesia’s main islands.

At an overwhelmed hospital in Sikakap, the main town on Pagai Utara island, doctors said they need medical supplies to help about 150 injured survivors. The hospital’s swelteringly hot rooms were filled with the moans of patients with flushed, sweat-coated faces.

"We need morphine," said Dr. Alyssa Scurrah, who flew in from Sydney, Australia. She said the hospital was desperate for a generator, antibiotics and a chest drain.

One of Scurrah’s patients was a 12-year-old girl who was struggling to breathe due to an open chest wound. She clenched her teeth and cried out as a doctor applied cotton pads to the gash along her rib cage.

The doctor said the girl needs to go to Padang for surgery, but no one could get off the island Saturday because of the weather.

"If she stays here, she may not live," Scurrah said.

One bright spot amid the misery: A baby girl was born at the hospital on Friday. The mother was caught in the wave as it slammed into her village, doctors said, but her injuries were not severe and she and her baby were expected to be fine.

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Associated Press writers Achmad Ibrahim and Kristen Gelineau in the Mentawai islands and Niniek Karmini in Jakarta contributed to this report.