A strong earthquake has struck the Indonesian island of Sulawesi.

The U.S. Geological Survey says the 6.6 magnitude quake struck late Saturday afternoon 56 kilometers from the town of Palu at a relatively shallow depth of 20 kilometers.

There are no immediate reports of damage or casualties. The French news agency reports panicked residents in Palu ran from their homes as the ground shook.

Indonesia is prone to earthquakes as it is located on the so-called Pacific Ring of Fire, which encircles the Pacific Basin.