Fresh artillery shots were heard on Friday on the tense South Korean island of Yeonpyeong, three days after it was devastated by a North Korean attack and hours after Pyongyang warned that the peninsula was on the brink of war.

The blasts happened just after the top U.S. commander in South Korea, Gen. Walter Sharp, toured Yeonpyeong Island in a show of solidarity with Seoul and to survey damage from Tuesday’s hail of North Korean artillery fire that killed four people.

An official at the South Korean Joint Chiefs of Staff said several new rounds of artillery fire were heard on Friday on Yeonpyeong, which is just seven miles (11 kilometers) south of the North Korean mainland. The military official, speaking on condition of anonymity, said several distant explosive sounds came from the direction of North Korea.

There were no immediate reports of damage.

AP photographers at an observation point on the northwest side of Yeonpyeong heard about four explosions, and said they witnessed at least one flash of light on the North Korean mainland.

South Korea’s YTN television network, citing an unidentified military official, said North Korea apparently was carrying out a military drill, and had fired up to 20 rounds. Yeonpyeong residents were fleeing to shelters, the report said. The report couldn’t be immediately confirmed.

Only a few dozen residents remained on Yeonpyeong, with most of the population of 1,300 fleeing in the hours and days after Tuesday’s attack and authorities urging them to evacuate.

Pyongyang’s state news agency said drills this weekend involving South Korean forces and a U.S. nuclear powered supercarrier in Yellow Sea waters amount to a reckless move to target the North.

“The situation on the Korean peninsula is inching closer to the brink of war,” the dispatch from the Korean Central News Agency said. “Gone are the days when verbal warnings are served only.”

North Korea’s army and people are “now greatly enraged” and “getting fully ready to give a shower of dreadful fire,” the agency said. “Escalated confrontation would lead to a war, and he who is fond of playing with fire is bound to perish.”

Gen. Sharp toured Yeonpyeong earlier on Friday, dressed in a heavy camouflage jacket and army fatigues and wearing a black beret. He walked down a heavily damaged street strewn with debris from buildings. Around him were charred bicycles and shattered bottles of soju, a kind of Korean alcoholic drink.

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