More than 400 people have been confirmed killed, many swept away, as tsunami waves triggered by a massive earthquake crashed into the Indonesian island of Sulawesi.
Authorities expect the toll to rise sharply on Sunday as news arrives from remote areas.
Indonesia's Vice President Jusuf Kalla said there are concerns the death toll could rise into the thousands as there is as yet no word from the city of of Donggala, where 300,000 people reside.
Indonesian men check the body of earthquake and tsunami victims as they look for their relatives at a police hospital in Palu, central Sulawesi. Source: AAP
Dozens of people were reported to be still trapped in the rubble of a hotel in the city of Palu, which was hit by waves up to six metres high following the 7.5 magnitude earthquake on Friday.
Hundreds had gathered for a festival on the city's beach when the wall of water smashed onshore at dusk, sweeping many to their deaths.
Indonesian President Joko Widodo was scheduled to visit evacuation centres in the city on Sunday.
Head of the national disaster management agency (BNPB) Willem Rampangilei said the death toll from Palu had reached 420 people, according to news website Kompas.
"It's estimated that 10,000 refugees are scattered in 50 points in Palu city," he was quoted by Kompas as saying.
"We are having difficulty deploying heavy equipment to find victims under the rubble of buildings because many of the roads leading to Palu city are damaged."
Earlier authorities had put the death toll at 384.
Amateur footage shown by local TV stations showed waves crashing into houses along Palu's shoreline, scattering shipping containers and flooding into a mosque in the city.
A general view of tsunami devastated area in Palu, Central Sulawesi, Indonesia. Source: AAP
Dozens of injured people were being treated in makeshift medical tents set up outdoors.
Photos confirmed by authorities showed bodies lined up along the street on Saturday, some in bags and some with their faces covered with clothes.
BNPB spokesman Sutopo Purwo Nugroho said the damage was extensive and thousands of houses, hospitals, shopping malls and hotels had collapsed.
A bridge was washed away and the main highway to Palu was cut off due to a landslide.
"The tsunami didn't come by itself, it dragged cars, logs, houses, it hit everything on land," Nugroho said.
Nugroho said that casualties and damage could be greater along the coastline for 300km north of Palu, an area called Donggala, which is closer to the epicentre of the quake.
Communications "were totally crippled with no information" from Donggala, Nugroho said.
Villagers pray at a temporary shelter following earthquakes and a tsunami in Palu, Central Sulawesi, Indonesia. Source: AAP
"We're now getting limited communications about the destruction in Palu city, but we have heard nothing from Donggala and this is extremely worrying," he said.
Red Cross said there are more than 300,000 people living in the area.
The military has started sending in cargo planes with aid from Jakarta and other cities, authorities said, but evacuees still badly needed food and other basic necessities.
An Australian Department of Foreign Affairs spokesperson said the government was not aware of any Australians affected by the disaster but was continuing to make inquiries with local authorities.
Australian Prime Minister Scott Morrison has tweeted his condolences, saying he was saddened to hear of the tragic event on Sulawesi and that Australia stands ready to assist.
'I just ran'
Dramatic video footage captured from the top floor of a parking ramp in Palu, nearly 80 kilometres from the quake's epicentre, showed waves 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, who like many Indonesians goes by one name.
About 17,000 people had been evacuated, the disaster agency said, and that figure is expected to rise.
The shallow 7.5 magnitude tremor was more powerful than a series of quakes that killed hundreds on the Indonesian island of Lombok in July and August.
A man surveys the damage following earthquakes and a tsunami in Palu, Central Sulawesi. Source: AP
Indonesian president Joko Widodo said the military was being called in to the region to help search-and-rescue teams get to victims and find bodies.
"This was a terrifying double disaster," said Jan Gelfand, a Jakarta-based official at the International Federation of Red Cross and Red Crescent Societies.
"The Indonesian Red Cross is racing to help survivors but we don't know what they'll find there."
The massive tremors were felt hundreds of kilometres away and there has been little word about casualties in Donggala, a region north of Palu where at least one person was reported dead in Friday's quakes.
"We have heard nothing from Donggala and this is extremely worrying," Gelfand said.
"There are more than 300,000 people living there. This is already a tragedy, but it could get much worse."
The quake hit just off central Sulawesi at a depth of 10 kilometres just before 1100 GMT -- early evening in Indonesia -- the US Geological Survey said. Such shallow quakes tend to be more destructive.
An aerial image of the coastal area of Palu city, central Sulawesi, Indonesia. Source: AAP
Pictures supplied by the disaster agency showed a badly damaged shopping mall in Palu where at least one floor had collapsed onto the storey below, while other photographs showed major damage to buildings and large cracks across pavements.
Video from the scene showed a landmark double-arched yellow bridge had collapsed with its two metal arches twisted as cars bobbed in the water below.
An AFP reporter on the scene saw widespread damage some 50 metres inland.
A key access road had been badly damaged and was partially blocked by landslides, the disaster agency said.
Some government planes carrying relief supplies had managed to land at the main airport in Palu, although officials said the airport would likely remain closed to commercial flights until Thursday.
Neighbouring Malaysia has offered to send help to Sulawesi, a government spokesman there told AFP, adding Malaysia "was waiting for Indonesia's reply."
