The tsunami up to 2 metres (six feet) high struck beaches as dusk fell in Palu, a sleepy but growing tourist resort, and the nearby fishing town of Donggala, closest to the epicenter of the quake 27 km away, officials said.
Quakes of similar magnitude can cause great damage to poorly built or badly designed structures, including the toppling of chimneys, columns and walls, according to USGS.
The U.S. Geological Survey said the natural disaster at a depth of 18 kilometers was centered about 30 km north of the central Sulawesi town of Donggala.
At least one person was known to have died.
The quake was larger in magnitude than the 2006 Yogyakarta natural disaster, which measured 6.4 in magnitude, and the recent 7.0-magnitude Lombok natural disaster in August.
Indonesian TV showed smartphone footage of a large wave hitting Palu, and people screaming and running in fear.
The tsunami struck the city of Palu on Friday evening, with houses swept away and families reported missing, disaster agency spokesman Sutopo Purwo Nugroho said.
A auto swept away by Friday's tsunami is seen stuck under a damaged building in Palu, Central Sulawesi, Indonesia.
Manchester United forecasts record revenue for 2019
The manager had also been angered by Pogba's criticism of his tactics in Saturday's 1-1 draw against Wolves at Old Trafford . Former Premier League midfielder Craig Burley says Mourinho made the right call taking away his leadership responsibilities.
Following the initial tremors, an early tsunami warning was issued by the Indonesian meteorological agency, but it was later lifted.
"People are encouraged to remain vigilant", Sutopo said.
The video comes as officials have confirmed a tsunami of up to two metres hit the city after a powerful natural disaster rocked central Sulawesi. The water smashed into buildings and a large mosque that crumpled under the force.
Photos confirmed by authorities showed bodies being lined up along the street on Saturday, some in bags and some with their faces covered with clothes.
The main shock rattled about three hours after a revised 6.0-magnitude quake jolted the area, killing one person and injuring 10 others with scores of houses damaged.
Between July 29 and August 19, at least 557 people died and nearly 400,000 were displaced by four earthquakes with intensities varying between 6.3 and 6.9 magnitude which struck Indonesia's Lombok island. Oil company Pertamina said its fuel depot in Donggala had been damaged in the incident though there was no oil spill.
Authorities say the huge wave hit the cities of Palu and Donggala, but it is not yet clear the amount of casualties.
Indonesia is prone to earthquakes because of the country's location in the "Ring of Fire", the arc of volcanoes and active fault lines in the Pacific Basin.