National Disaster Mitigation Agency spokesman Sutopo Purwo Nugroho says a magnitude 7.5 earthquake that hit the island of Sulawesi caused a tsunami that hit Palu, the provincial capital, and Donggala.

Palu airport was closed.

Nugroho said in a live TV interview on Friday that houses were swept away and families are reported missing.

He said communications with the area in central Sulawesi are down and the search and rescue effort is being hampered by darkness.

The earthquake prompted a tsunami alert, but the alert was lifted within an hour.

Earlier, a milder quake destroyed some houses, killing one person and injuring at least 10 in Donggala, authorities said.

More than 600,000 people live in Donggala and Palu.

"The (second) quake was felt very strongly, we expect more damage and more victims," Nugroho said, adding that evacuation process is still ongoing.

Based on initial reports, "many buildings" collapsed due to the 7.5 magnitude quake, he said.

A series of earthquakes in July and August killed nearly 500 people on the holiday island of Lombok, hundreds of kilometres southwest of Sulawesi.

Indonesia sits on the Pacific Ring of Fire and is regularly hit by earthquakes.

In 2004, an earthquake off the northern Indonesian island of Sumatra triggered a tsunami across the Indian Ocean, killing 226,000 people in 13 countries, including more than 120,000 in Indonesia.

Australian Associated Press