At least 384 people have died after an earthquake-spawned tsunami swept away buildings on the central Indonesian island of Sulawesi.
Damaged roads and broken lines of communication hampered rescue efforts as team attempt to reach devastated areas.
Disaster agency spokesman Sutopo Purwo Nugroho said all 384 people known to have died were killed in the city of Palu alone.
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 remains unknown.
The nearby city of Donggala and the town of Mamuju were also ravaged by the magnitude 7.5 earthquake and subsequent tsunami but had not yet been reached by aid.
In some places, the water rose as high as six meters (20 feet).
Palu, home to more than 380,000 people, was strewn with debris from collapsed buildings. A mosque heavily damaged by the quake was half submerged and a shopping mall was reduced to a crumpled hulk, while a large bridge with yellow arches had collapsed.
The city is built around a narrow bay that apparently magnified the force of the tsunami waters as they raced into the tight inlet.
Indonesian TV showed dramatic footage of a powerful wave hitting Palu, with people screaming and running in fear. The water smashed into buildings and the damaged mosque.
Hundreds of people were injured and hospitals, damaged by the quake, have been overwhelmed by the casualties.
Officials hope satellites crossing over Indonesia can capture images and provide rescuers with information so they know where to send humanitarian aid.
Indonesia is a vast archipelago of more than 17,000 islands that is home to 260 million people. Roads and infrastructure are poor in many areas, making access difficult in the best of conditions.
The disaster agency has said that essential aircraft can land at Palu’s airport, though AirNav, which oversees aircraft navigation, said the runway was cracked and the control tower damaged.
AirNav said one of its air traffic controllers, aged 21, died in the quake after staying in the tower to ensure a flight he’d just cleared for departure got airborne safely.
More than half of the 560 inmates in a Palu prison fled after its walls collapsed during the quake, said its warden, Adhi Yan Ricoh.
“It was very hard for the security guards to stop the inmates from running away as they were so panicked and had to save themselves too,” he told state news agency Antara.
Ricoh said there was no immediate plan to search for the inmates because the prison staff and police were consumed with the search and rescue effort.
United Nations spokesman Stephane Dujarric said UN officials were in contact with Indonesian authorities and “stand ready to provide support as required”.
Indonesia, the world’s most populous Muslim country, is frequently hit by earthquakes, volcanic eruptions and tsunamis because of its location on the “Ring of Fire,” an arc of volcanoes and fault lines in the Pacific Basin.
In December 2004, a massive magnitude 9.1 earthquake off Sumatra island in western Indonesia triggered a tsunami that killed 230,000 people in a dozen countries.
On August 5 a powerful quake on the Indonesian island of Lombok killed 505 people, most of whom died in collapsing buildings.