The 7.5 magnitude quake occurred at a shallow depth of 10km (6.2 miles) just off the central island of Sulawesi at 18:03 (10:03 GMT), triggering a tsunami, US monitors say.
Many people were on the beach in Palu, preparing for a festival, and were caught when waves up to 3m (10ft) in height swept in. Haris, who was in the city for a wedding, was staying in a hotel with his wife and daughter when the quake struck.
"There was no time to save ourselves," he told the Associated Press news agency. "I was squeezed into the ruins of the wall... 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."
With back and shoulder injuries, he is being treated outdoors at Palu's Army Hospital. ...