JAKARTA, Indonesia (AP) — Two powerful and shallow undersea earthquakes shook western Indonesia on Wednesday, causing panic but no immediate reports of casualties or damage.

The U.S. Geological Survey said the magnitude 6.8 earthquake occurred at a depth of 22 kilometers (13.6 miles) under the sea. It was centered in Bengkulu province on Sumatra island, 139 kilometers (86 miles) west-southwest of Bengkulu city, USGS said. It was felt in several provinces on the island.

A 6.9 magnitude quake jolted the area six minutes later, a bit deeper and 13 kilometers (8 miles) from the first, but no tsunami warning was issued for the relative shallow quakes.

Indonesia, a vast archipelago of 270 million people, is frequently struck by earthquakes, volcanic eruptions and tsunamis. It is located on the “Ring of Fire,” an arc of seismic faults in the Pacific Basin where most of the world’s earthquakes occur.