A 6.6-magnitude earthquake has hit Indonesia's central Sulawesi province, the US Geological Survey said, sending terrified residents fleeing into the streets.

No tsunami warning has been issued and there were no immediate reports of damages or casualties after the quake on Saturday.

"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 the AFP.

The quake struck on land 56km southeast of the city of Palu at around 0940 GMT at a depth of 20km.

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

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

Indonesia is prone to earthquakes because it is in the Pacific Ring of Fire, an arc of volcanoes and fault lines encircling the Pacific Basin.

Source: Agencies