A powerful underwater earthquake struck western Indonesia on Sunday, injuring four people as they tried to flee, officials said.

Indonesia's meteorological and geophysics agency said no tsunami warning was issued.

The U.S. Geological Survey said the quake registered magnitude 6.7, after initially measuring it at 7.0. It struck at 2:38 p.m. and was centered at a depth of 28 miles under the Indian Ocean seabed, about 70 miles west-southwest of the city of Padang on Sumatra island, it said.

Four people were injured as they fled in Padang and a house was damaged, said Ade Edward, a local government official.

Indonesia straddles a chain of fault lines and volcanoes known as the Pacific "Ring of Fire" and is prone to seismic activity. A huge quake off western Indonesia caused a powerful tsunami in 2004 that killed around 230,000 people in a dozen countries.