Tears filled Dwi Haris's eyes as he recalled the moment a violent earthquake shook the hotel room he shared with his family — somehow, he was spared, but he has no idea what has become of his wife or daughter.

Key points:

• Sulawesi struck first by magnitude-7.5 quake, followed by tsunami
• Hard-hit area of Palu is home to more than 380,000 people
• Hospitals treating patients outdoors due to continuing aftershocks

Mr Haris is among the survivors of Indonesia's latest natural disaster.

Residents, too afraid to sleep indoors, camped out in the darkness on Saturday while victims recounted harrowing stories of being separated from their loved ones a day after a powerful earthquake triggered a tsunami that unleashed waves as high as six metres, killing hundreds on the Indonesian island of Sulawesi.

The head of the National Disaster Management Agency (BNPB), Willem Rampangilei, said late on Saturday the death toll from Palu had reached 420 people, according to news website Kompas.

Hundreds of people were injured and hospitals, damaged by the magnitude-7.5 quake, were overwhelmed.

A doctor examines an injured child outside at Army hospital.

Some of the injured, including Mr Haris, who suffered a broken back and shoulder, rested outside Palu's Army Hospital, where patients were being treated outdoors due to continuing strong aftershocks.

He welled up as he recounted the quake.

"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."

The family was in town for a wedding.

'I heard people shouting Water! Water'

Nina, a 23-year-old woman who goes by one name, was working at a laundry service shop not far from the beach when the quake hit.

She said it destroyed her workplace, but she managed to escape and quickly went 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."

The earthquake left mangled buildings with collapsed awnings and metal sticking out of concrete like antennae.

Roads were buckled and cracked.

Indonesian men walk past the wreckage of a car.

The tsunami created even more destruction.

It was reported as being three metres high in some areas and double that height elsewhere.

"We got a report over the phone saying that there was a guy who climbed a tree up to six metres high," disaster agency spokesman Sutopo Purwo Nugroho said.

Festival-goers' fate unknown

Mr Nugroho previously said the death toll was expected to rise once rescuers were able to reach surrounding coastal areas.

He said other people were unaccounted for, without giving an estimate.

Mr Nugroho said "tens to hundreds" of people were taking part in a beach festival in Palu when the tsunami struck at dusk on Friday. Their fate was unknown.

Palu, which has more than 380,000 people, was strewn with debris from the earthquake and tsunami.

A mosque heavily damaged by the quake was half submerged and a shopping mall was reduced to a crumpled hulk.

A large bridge with yellow arches had collapsed.

Bodies lay partially covered by tarpaulins and a man carried a dead child through the wreckage.

The city is built around a narrow bay that apparently magnified the force of the tsunami waters as they raced into the tight inlet.

People injured or affected by the earthquake and tsunami wait to be evacuated on an air force plane in Palu.

Indonesian TV showed dramatic smartphone video of a powerful wave hitting Palu, with people screaming and running in fear. The water smashed into buildings and the mosque.

The cities of Donggala and Mamuju, near Palu, were also ravaged, but little information was available due to damaged roads and disrupted telecommunications.