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This article is more than 1 year old

The confirmed death toll from the earthquake and tsunami that struck the Indonesian island of Sulawesi has risen to 832, and the vice-president, Jusuf Kalla, has warned it could reach into the thousands.

More than 150 aftershocks followed the 7.5-magnitude earthquake and subsequent tsunami that hit Sulawesi on Friday, causing thousands of homes, hotels, shopping malls and several mosques to collapse.

Of the fatalities, 821 were in the city of Palu, with 11 casualties so far recorded in Donggala, the worst-hit area, which is home to 300,000 people. Hundreds of bodies have been found on beaches and authorities fear many may have been washed out to sea.

Speaking at a press conference, Sutopo Purwo Nugroho, the spokesman for the BNBP disaster agency, said the area affected was much bigger than originally thought.

“The deaths are believed to be still increasing since many bodies were still under the wreckage while many have not able to be reached,” said Sutopo, emphasising that access to Donggala, as well as the towns of Sigi and Boutong, was very limited so the final death toll was impossible to predict.

The city of Palu has been completely devastated by the earthquake and tsunami waves, which reached as high as six metres in some areas. In the city, partially covered bodies lay near the shore and survivors sifted through a tangled mess of corrugated steel roofing, timber, rubble and flotsam. One man was seen carrying the muddy corpse of a small child.

“Many corpses are scattered on the beach and floating on the surface of the sea,” one local resident, Nining, told local media. The identified bodies are being buried in mass graves, Sutopo said.

Sutopo confirmed there was no electricity in Palu and Donggala, while drinking water and fuel were running out. There was limited access to heavy equipment needed to help rescue efforts, so the search for people trapped in the rubble was mostly being carried out by hand.

Rescue efforts are continuing for dozens of people still trapped in the collapsed ruins of the eight-storey Roa Roa hotel in Palu, with voices heard screaming from the wreckage.

A 25-year-old woman was found alive during the evening in the ruins of the Roa-Roa Hotel, according to the National Search and Rescue Agency, which released photos of the her lying on a stretcher covered in a blanket.

There were concerns about the whereabouts of hundreds of people preparing for a beach festival that had been due to start on Friday, a spokesman for the BNBP said.

Play Video 1:00 Drone captures aftermath of tsunami on Indonesian island - video

Aerial footage shows tsunami destruction in Sulawesi – in pictures Read more

At least 540 people had been badly injured, the agency said, as hospitals struggled to cope with the influx of casualties, setting up open-air clinics to treat the injured.

Dwi Haris, who suffered a broken back and shoulder, rested outside Palu’s army hospital, where patients were being treated outdoors due to the continuing strong aftershocks. Tears filled his eyes as he recounted feeling the violent earthquake shake the fifth-floor hotel room he shared with his wife and daughter.

“There was no time to save ourselves. I was squeezed into the ruins of the wall, I think,” said Haris, adding that his family was in town for a wedding. “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.”

The Indonesian president, Joko Widodo, who visited the region on Sunday, said earlier the military was being called to the region to help search-and-rescue teams.

Aerial footage shows tsunami destruction in Sulawesi – in pictures Read more

One of the first casualties of the earthquake, 21-year-old Anthonius Gunawan Agung, is being hailed a hero after he stayed in the air traffic control tower as the earthquake hit, to make sure that a flight to Bali could take off safely. Agung then jumped from the control tower as it was collapsing, but did not survive the fall.

Many residents slept in makeshift shelters, terrified that the powerful aftershocks could topple their damaged homes.

Facebook Twitter Pinterest Villagers view a ship swept ashore by tsunami in Palu, Central Sulawesi, Indonesia. Photograph: Rio Mario/AP

Some voiced criticism of the agency that lifted the tsunami warning. The agency said it followed standard operating procedure and made the call to “end” the warning based on data available from the closest tidal sensor, about 125 miles (200km) from Palu.

“We have no observation data at Palu. So we had to use the data we had and make a call based on that,” said Rahmat Triyono, the head of the earthquakes and tsunami centre at BMKG. He said the closest tide gauge, which measures changes in the sea level, only recorded an “insignificant” 6cm wave and did not account for the giant waves near Palu.

We have heard nothing from Donggala and this is extremely worrying Jan Gelfand, Red Cross

The tsunami was triggered by a strong quake that brought down buildings and sent locals fleeing for higher ground as a churning wall of water crashed into Palu. “We all panicked and ran out of the house” when the quake hit, said Anser Bachmid, a 39-year-old Palu resident. “People here need aid – food, drink, clean water.”

Dramatic video footage captured from the top floor of a parking ramp in Palu, nearly 50 miles (80km) from the quake’s epicentre, showed waves bring down several buildings and inundate a large mosque.

Play Video 1:06 Massive wave hits Palu in Indonesia – video

About 17,000 people have been evacuated, the BNBP said.

“This was a terrifying double disaster,” said Jan Gelfand, a Jakarta-based official at the International Federation of Red Cross and Red Crescent Societies. “We have heard nothing from Donggala and this is extremely worrying. There are more than 300,000 people living there. This is already a tragedy, but it could get much worse.”

Friday’s tremor was also felt in the far south of the island in its largest city Makassar and on neighbouring Kalimantan, Indonesia’s portion of Borneo island.

The initial quake struck as evening prayers were about to begin in the world’s biggest Muslim-majority country on the holiest day of the week, when mosques are especially busy.

Indonesia is one of the most disaster-prone nations on earth. It lies on the Pacific “Ring of Fire”, where tectonic plates collide and many of the world’s volcanic eruptions and earthquakes occur.

Earlier this year, a series of powerful quakes hit Lombok, killing more than 550 people on the holiday island and neighbouring Sumbawa.

Indonesia has been hit by a string of other deadly quakes including a devastating 9.1-magnitude tremor that struck off the coast of Sumatra in December 2004.

That Boxing Day quake triggered a tsunami that killed 220,000 throughout the region, including 168,000 in Indonesia.