The strong shaking sent people fleeing into open areas in and around Palu, a city of about 400,000 people and the capital of Central Sulawesi province. Several hospitals evacuated patients, some with IV drips, outdoors as a safety measure.

Images from the area showed heavily damaged structures with partially collapsed roofs, shattered walls and debris scattered across the streets. The National Disaster Management Agency said information on the damage, possible casualties and displaced people was still being gathered.

"We have evacuated all guests from the hotel, including several guests who remained in their rooms," said Effendi Natali, a general manager of a four-star hotel in Palu.

"They all panicked, which is a natural reaction during an earthquake, but everyone is safe," Natali said, adding that the hotel sustained only minor damage.

The initial quake was centered 43 kilometers (27 miles) east-southeast of Palu, and the U.S. Geological Survey said it was about 10 kilometers (6 miles) deep. Several aftershocks followed, the strongest being 5.2 magnitude.

People also moved away from coastal areas as a precaution if the quake set off a tsunami. Indonesia's Meteorology, Climatology, and Geophysical Agency said there was no danger of a tsunami but warned aftershocks could continue.