China, which is North Korea’s main political ally, urged restraint and called on both sides to resume talks.
Yeonpyeong, about 120 km (75 miles) west of Seoul, is home to more than 2,000 residents and troops stationed there and can be reached by boats, which take more than 2-1/2 hours.
Leif-Eric Easley, a professor of international studies at Ewha University in Seoul, said it is not unusual for North Korea to fire artillery into the area during winter drills.
“What’s different this year is that Kim Jong Un has publicly rejected rapprochement and unification with the South,” he said.
In remarks at a major party meeting last week, the North Korean leader said unification with the South was not possible and that Pyongyang was fundamentally changing its policy toward the South, which it now views as an enemy state.
The waters near the disputed NLL have been the site of several deadly skirmishes between North and South Korea, including a battle involving warships and the sinking of a South Korean corvette by North Korean torpedoes in 2010, which killed 46 sailors.
In November 2010, North Korean artillery fired several dozen rounds on Yeonpyeong Island, killing two soldiers and two civilians, one of the heaviest attacks on its neighbor since the Korean War ended in 1953.