Dawn revealed a devastated coastline in central Sulawesi where the 3-meter high (10 foot) tsunami triggered by a magnitude 7.5 earthquake Friday smashed into two cities and several settlements.

Disaster agency spokesman Sutopo Purwo Nugroho said in a television interview there are "many victims."

In Palu, the capital of Central Sulawesi province, the city of more than 380,000 people was strewn with debris from collapsed buildings.

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

An AP reporter saw bodies partially covered by tarpaulins and a man carrying a dead child through the wreckage.

In the nearby city of Donggala a large bridge spanning a coastal river had collapsed.

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

Communications with the area are difficult because power and telecommunications are cut, hampering search and rescue efforts.

Nugroho said the runway of Palu's airport is not damaged and essential aircraft can land there.

Indonesia's president on Friday night said he had instructed the security minister to coordinate the government's response to a quake and tsunami that hit central Sulawesi.

Joko "Jokowi" Widodo also told reporters in his hometown of Solo that he had called on the country's military chief help with search and rescue efforts.

UN spokesman Stephane Dujarric said UN officials were in contact with Indonesian authorities and "stand ready to provide support as required."

Indonesia is prone to earthquakes 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 in western Indonesia triggered a tsunami that killed 230,000 people in a dozen countries. (AP)