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

The US Geological Survey said the magnitude 6.8 earthquake occurred at a depth of 10 kilometers (6.2 miles) under the sea. It was centered in Bengkulu province on Sumatra island, 144.5 kilometers (89.6 miles) west-southwest of Bengkulu city, USGS said. It also was felt in several provinces on the island.

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Similar earthquake with 6.9 magnitude jolted the province six minutes later, but no tsunami warning was issued for the relative shallow quakes.

“We were awakened by repeated strong shaking of quakes at dawn,” a Bengkulu resident wrote in Twitter, “Forcing us to run out of our house.”

Indonesia, a vast archipelago of 270 million people, is frequently struck by earthquakes, volcanic eruptions and tsunamis because of its location on the “Ring of Fire,” an arc of volcanoes and fault lines in the Pacific Basin.