South Korea’s military says that the sound of artillery was heard on Yeonpyeong Island.

South Korea’s Joint Chiefs of Staff said that one artillery round was heard Sunday from a North Korean military base north of the sea border dividing the two Koreas. It was not immediately clear where the round landed.

Earlier residents of the island were ordered to take shelter.

Four South Koreans died last week after the North rained artillery on the small Yellow Sea island, which is home to both fishing communities and military bases.

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