The national disaster agency on Saturday put the official death toll so far at 384, all of them in the tsunami-struck city of Palu, but warned the number was likely to rise.
In the city – home to around 350,000 people – partially covered bodies lay on the ground near the shore, the day after tsunami waves 1.5 metres came ashore.
There were also concerns over the whereabouts of hundreds of people preparing for a beach festival due to start Friday evening, the disaster agency said.
Hospitals were overwhelmed by the influx of injured, with many people being treated in the open air, while other survivors helped to retrieve the remains of those who died.
The city, built around a narrow bay that apparently magnified the force of the tsunami waters, was strewn with debris from collapsed buildings.
Seawater pooled inland and a mosque heavily damaged by the quake was half submerged. A shopping mall in the paralysed city had been reduced to a crumpled hulk.
The tsunami, triggered by a 7.5 magnitude earth quake, smashed into Sulawesi island at dusk on Friday.
Sutopo Purwo Nugroho, spokesman for Indonesia’s disaster agency, described the damage from the quake and tsunami as “extensive” and said bodies of some victims were found trapped between rubble of collapsing buildings.
In the nearby city of Donggala, a large bridge with yellow arches that spanned a coastal river had collapsed.
Disaster agency reported ‘extensive’ damage to buildings in Palu.
Dramatic video footage filmed from the top floor of a parking ramp in Palu, nearly 80km from the quake’s epicentre, showed waves of water bring down several buildings and inundate a large mosque.
“I just ran when I saw the waves hitting homes on the coastline,” said Palu resident Rusidanto.
The quake and tsunami caused a major power outage that cut communications around Palu and on Saturday authorities were still having difficulties coordinating rescue efforts.
Road access to Palu from the east and the south were also disconnected.
The city’s airport remained closed after its runway and air traffic control tower was damaged in the quake but officials said they were preparing to reopen to allow aid to come in.
Indonesian president Joko Widodo said the military was being called in to the disaster-struck region to help search-and-rescue teams get to victims and find bodies.
“Makeshift shelters are being erected in the cities nearby. For now, the majority of people there are staying outside their homes,” he added.
Indonesia’s meteorological and geophysics agency BMKG issued a tsunami warning after the quake, but lifted it 34 minutes later.
The agency was widely criticised for not informing a tsunami had hit Palu on Saturday, though officials said waves had come within the time the warning was issued.
The Palu area was hit by a less powerful quake earlier on Friday, which destroyed some houses, killed one person and injured at least 10 in the fishing town of Donggala, closest to the epicentre, authorities said.
Indonesia sits on the Pacific Ring of Fire and is regularly hit by earthquakes. In August, a series of major quakes killed over 500 people in the tourist island of Lombok and destroyed dozens of villages along its northern coast.