PALU, Indonesia — Rescuers in Indonesia were scrambling on Sunday to reach people calling for help from collapsed buildings after a devastating earthquake spawned a tsunami that left more than 800 dead.
“I can still hear the voices of the survivors screaming,” Muhammad Syaugi, the head of Indonesia’s search and rescue agency, told a local news outlet, Detik.com, after visiting the site of a toppled hotel in Palu, on the island of Sulawesi. He added that 50 people could be trapped in the wreckage of the eight-story building.
The disaster agency spokesman, Sutopo Purwo Nugroho, said at a news conference on Sunday that the death toll from Friday’s twin disasters had more than doubled to 832, with nearly all of the reported deaths in Palu. That number was almost certain to rise, he added, as many surrounding coastal areas still were not able to report fully on casualties.
“Many bodies were still under the wreckage, while many have not been reached,” he said.
Aid and supplies were being sent to badly affected areas using military and commercial aircraft, including helicopters.
The cities of Donggala, the site closest to the earthquake’s epicenter, and Mamuju were also ravaged, but little information was available because of damaged roads and disrupted telecommunications. Footage from MetroTV on Sunday showed images of destroyed houses in Donggala and areas that were once land now inundated with water. Aerial video also showed the battered coastline surrounding Palu.
President Joko Widodo was set to visit the area later Sunday.
Looters were stealing on Sunday from a badly damaged mall in Palu that was unguarded, apparently unconcerned about its safety despite continuing aftershocks. Residents were also seen returning to their destroyed homes and picking through waterlogged belongings, trying to salvage anything they could.
Mr. Nugroho said “tens to hundreds” of people had been taking part in a beach festival in Palu when the tsunami struck at dusk on Friday. Their fates were unknown.
Hundreds of people in the area were injured, and hospitals, many of them damaged by the magnitude-7.5 quake, were overwhelmed. Some patients were being treated outdoors because of strong aftershocks.
Dwi Haris, whose back and shoulder were broken, rested outside Palu’s Army Hospital. He tearfully recounted feeling shaking of the hotel where his family had been staying as they visited Palu for a wedding.
“There was no time to save ourselves. I was squeezed into the ruins of the wall, I think,” Mr. Haris said. “I heard my wife cry for help, but then silence. I don’t know what happened to her and my child. I hope they are safe.”
Indonesia is frequently struck by earthquakes, volcanic eruptions and tsunamis because of its location on the Ring of Fire, an arc of volcanoes and fault lines in the Pacific Basin. In December 2004, a magnitude-9.1 earthquake off the western island of Sumatra set off a tsunami that killed 230,000 people in a dozen countries. In August, a powerful quake off the island of Lombok killed 505 people.
Palu, a city of more than 380,000, is built around a narrow bay that apparently magnified the force of the tsunami waters as they raced into the tight inlet.
Indonesian television showed dramatic smartphone video of a powerful wave hitting Palu, with people screaming and running in fear. The water smashed into buildings, tearing many apart. On Sunday, the city was strewn with debris, and bodies lay covered by tarpaulins.
Nina, a 23-year-old woman who goes by one name, was working at a laundry service not far from the beach when the quake hit. She said it destroyed the shop, but she managed to escape and raced home to get her mother and younger brother.
“We tried to find shelter, but then I heard people shouting, ‘Water! Water!’” she recalled, crying. “The three of us ran, but got separated. Now I don’t know where my mother and brother are. I don’t know how to get information. I don’t know what to do.”
Indonesia is a vast archipelago of more than 17,000 islands that are home to 260 million people. Roads and infrastructure are poor in many areas, making access difficult in the best of conditions. The earthquake and tsunami left mangled buildings and buckled roads. Communications with the area were difficult because power was out, hampering search and rescue efforts. Most people slept outdoors, fearing the aftershocks.
“We hope there will be international satellites crossing over Indonesia that can capture images and provide them to us so we can use the images to prepare humanitarian aid,” said Mr. Nugroho, the disaster agency spokesman.
In the chaos, more than half of the 560 inmates in a Palu prison fled after its walls collapsed, said its warden, Adhi Yan Ricoh.
“It was very hard for the security guards to stop the inmates from running away, as they were so panicked and had to save themselves too,” he told the state news agency, Antara.
Mr. Ricoh said there was no immediate plan to search for the inmates because the prison staff and police were consumed with the rescue efforts.
“Don’t even think to find the inmates. We don’t even have time yet to report this incident to our superiors,” he said.