By AUBREY BELFORD
JAKARTA, Indonesia — Indonesian rescue workers struggled against rough weather and difficult terrain to reach tsunami victims on Thursday as the death toll continued to rise from the natural disasters that hit the archipelago nation this week on two separate fronts and just 24 hours apart.
In the remote Mentawai Islands west of Sumatra, aid workers said that the isolation of many villages as well as choppy seas meant that some victims had yet to receive any assistance three days after a magnitude 7.7 underwater quake sent a 10-foot-tall tsunami crashing onto land, smashing apart homes and killing hundreds.
As a steady trickle of supplies reached the islands with the help of military ships and aircraft, officials raised the toll to 343 confirmed dead and 338 missing. An estimated 16,000 people have been displaced, officials said.
At the same time, a new eruption on Thursday evening at Mount Merapi on the island of Java, about 750 miles to the east, stirred fears of further destruction. Powerful eruptions late Tuesday killed 34 people and destroyed villages in clouds of superheated gas and debris, said Nelis Zuliasri, a spokeswoman for the National Disaster Management Agency.
Nearly 40,000 villagers who had fled plumes of hot ash were being asked to stay in temporary shelters while seismologists tried to determine whether the fresh eruptions meant that further destruction was on the way. There had been no reports of anyone hurt in the latest eruption, Ms. Zuliasri said.
In the Mentawai Islands, which are among the most underdeveloped areas of Indonesia, aid workers said that assistance was still only trickling in to many hard-hit but hard-to-reach islands. “We’re still just trying to fulfill the basic needs — food, tents, blankets, things like that,” Ms. Zuliasri said. “We’ve sent medicine out there, and we’re now using Hercules aircraft and ships.”
“Based on reports from this afternoon, there are some villages that we haven’t been able to get assistance to,” she said.
Photographs showed rescuers, some wearing face masks, carrying corpses in yellow body bags in Pororogat on South Pagai Island, one of the Mentawais. On the island of Pagai Seatandug, The Associated Press reported, the body of a village pastor was found under mud and palm fronds. Police officers and relatives took turns burrowing into sodden dirt nearby for his grave.
There were surprising tales of survival, as well. An 18-month-old baby was found alive in a clump of trees on Pagai Selatan island on Wednesday, The A.P. reported. Harmensyah, head of the West Sumatra provincial disaster management center, was quoted as saying that a 10-year-old boy had found the toddler.
Some survivors recalled the first moments of the tsunami. Joni Sageru, 30, a fisherman on the island of Pagai Selaton, told The A.P. that he was awakened by the quake and then heard screams urging everyone to run to higher ground.
“First, we saw seawater recede far away,” Mr. Sageru said. “Then, when it returned, it was like a big wall running toward our village. Suddenly trees, houses and all things in the village were sucked into the sea and nothing was left.”
President Susilo Bambang Yudhoyono flew by helicopter to the Mentawais to inspect the aid effort. He had cut short a visit to Vietnam and skipped a summit meeting of Southeast Asian leaders that began Thursday.
Anggraeni Puspitasari, a local aid coordinator for the charity World Vision, said that poor weather was causing transport bottlenecks and slowing down aid and that the danger of disease was rising.
“The local government has provided two speedboats, but yesterday we were only able to get one out there,” she said from the West Sumatran capital city, Padang. “Today, only one could go as well. It’s because the weather is still unstable.”
The Indonesian authorities confirmed that there was no comprehensive system for delivering an early tsunami warning to the Mentawais, but that was because the islands were too close to fault lines to get a warning in time to do any good.
“There is no technology that could give a warning in under five minutes,” said Ade Edward, head of operations for the Disaster Management Agency in West Sumatra Province. Two buoys that are part of the country’s tsunami warning system were out of commission, because of earlier vandalism, when the tsunami struck late Monday, according to Suharjono, the technical chief of Indonesia’s Meteorology, Climatology and Geophysics Agency. But he said that the system had still successfully sent out a nationwide warning within five minutes.
Cities and towns on the Sumatran mainland, including Padang, received alerts, Mr. Suharjono said.
Hundreds of people, including politicians, attended the funeral of Penewu Suraksohargo, popularly known as Mbah Maridjan, who was long honored for what was believed to be a supernatural connection with Mount Merapi. He did not leave his village when the evacuation was ordered. Some Indonesian newspapers have reported that he felt he had to stay to use his powers to keep the damage to a minimum.
The Jakarta Globe, in an obituary, said that a friend who visited a few days before the eruption related that Mbah Maridjan had said “he couldn’t because he had a responsibility, and that because ‘My time to die in this place has almost come — I can’t leave.’ ”
Fifteen people were killed with him when superheated gases and hot ash destroyed the village.
Henry Fountain contributed reporting from New York.