PALU, Indonesia: A 6.6-magnitude earthquake hit Indonesia's central Sulawesi province on Saturday, the U.S. Geological Survey said, sending terrified residents fleeing into the streets.

The quake struck on land 56 kilometres (35 miles) southeast of the city of Palu at around 5:40 pm (0940 GMT) at a depth of 20 kilometres (12 miles).

Panicked residents in Palu ran from their homes as the ground shook violently for a few seconds, an AFP reporter said.

"We've received no reports of damage or casualties... We'll continue monitoring," Indonesia's Meteorology, Climatology and Geophysics Agency technical chief Suharjono, who like many Indonesians goes by one name, told AFP.

The Indonesian agency earlier reported the quake's magnitude at 6.2 at a depth of 10 kilometres (six miles), with its epicentre in the populated mountainous district of Parigi Moutong.

Indonesia sits on the Pacific "Ring of Fire" where continental plates collide, causing frequent seismic and volcanic activity.