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SEOUL, South Korea — A 5.4 magnitude earthquake shook South Korea's southeastern coastal region Wednesday afternoon, breaking some windows and crumbling walls near the epicenter. No casualties were reported.

The quake was centered off the coast about 9.3 kilometers (5.8 miles) northwest of the port city of Pohang, according to the U.S. Geological Survey. South Korea's state-run Korea Meteorological Administration measured the quake at the same strength but said the epicenter was inside Pohang.

Residents in the capital, more than 300 kilometers (186 miles) away, felt tremors and said their buildings shook.

South Korean media showed crumbled walls piled on parked cars, broken windows from some buildings and elementary school students taking shelter on a playground.

No injuries or major damage has been reported, according to the Korea Meteorological Administration.

It's the strongest quake in South Korea since a 5.8-magnitude occurred near the ancient city of Gyeongju, which is close to Pohang, in September 2016, Korea Meteorological Administration officials said.

South Korea has relatively little seismic activity, unlike neighboring Japan.