QUESTIONS ABOUT WARNINGS

Indonesia is all too familiar with deadly earthquakes and tsunamis. In 2004, a quake off Sumatra island triggered a tsunami across the Indian Ocean, killing 226,000 people in 13 countries, including more than 120,000 in Indonesia.

Questions are sure to be asked why warning systems set up around the country after that disaster appear to have failed on Friday.

The meteorological and geophysics agency BMKG issued a tsunami warning after the Friday quake but lifted it 34 minutes later, drawing widespread criticism it had withdrawn it too quickly. But officials said they estimated the waves had hit while the warning was in force.

Hundreds of people had gathered for a festival on Palu's beach when the wall of water smashed onshore at dusk on Friday, sweeping many people to their deaths.

Video footage showed trees, buildings and a communications tower being swept through a rural landscape by a landslide caused by liquification of the soil, according BNPB's Nugroho.

In other footage on social media, a man on the upper floor of a building could be heard shouting warnings of the approaching tsunami to people on the street below moments before the wave crashed ashore.

The Head of the National Disaster Management Agency (BNPB), Willem Rampangilei, told reporters in Sulawesi late on Saturday rescuers were struggling in their hunt for more victims as the death toll in Palu had reached 420.

"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," he was quoted by the Kompas newspaper as saying.

About 10,000 displaced people were scattered at 50 different places in Palu, he said.

Amateur video footage aired by TV stations showed waves crashing into houses along Palu's shoreline, scattering shipping containers and flooding into a mosque.

Dozens of injured people were being treated in tents set up in the open.