Seoul: North Korea conducted a firing drill on its western coast, hours after observers heard an explosive sound near the frontline island of Baengnyeong, South Korea's military confirmed on Saturday.
The military said North Korea fired artillery "several times" from its western coast, Yonhap news agency reported.
The firing, however, did not cross the maritime border in the Yellow Sea, widely known as the Northern Limit Line (NLL), it said.
Residents were asked to remain alert for a possible evacuation, while nearby fishing boats were also requested to return to their ports, it added.
The military added it will continue to keep a close eye on North Korea, especially at the NLL. There have been no significant moves in the North since the firing, it said.
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In November 2010, North Korea fired some 170 rounds of artillery at another frontline island of Yeonpyeong, killing two South Korean marines, two civilians and injuring 16 others.
Pyongyang's provocations have continued since early 2016.
North Korea conducted what it claimed to be a successful test of an H-bomb on January 6. Earlier this month, it also launched a satellite, which was viewed by many as a cover for testing its intercontinental ballistic missile technology.
South Korea closed down the inter-Korean industrial zone in the North Korean border city of Kaesong earlier this month in response to North Korea's moves.