North Korea staged artillery drills Friday that sent some South Koreans scrambling for bomb shelters, as South Korea and the U.S. geared up for naval exercises they say will send a clear message to Pyongyang.

South Korean navy ships sail near the Yeonpyeong Island, South Korea, on Friday. North Korea fired artillery shells near the island, as tensions continue to run high on the peninsula. (Lee Jin-man/Associated Press)

North Korea, which said the naval drills will push the peninsula closer to war, fired a barrage of about 20 artillery shells just across from Yeonpyeong Island, the target it hit on Tuesday, killing four people and destroying dozens of homes.

U.S. Gen. Walter Sharp, the senior American military commander in the region, toured the island Friday to inspect the damage.

"It is clear to me by the briefings that I have received and by what I've seen here physically that North Korea attacked this island," he said.

Sharp did not hear North Korea's show of might Friday, and none of the rounds hit the South, though residents on other parts of the island panicked and headed back into air raid shelters.

An aircraft carrier, the USS George Washington, will arrive near the island on the weekend and participate in live fire exercises with South Korea's military. Washington keeps more than 28,000 troops in South Korea, a legacy of the Korean war and a sore point with the north.

Gen. Walter Sharp, centre, commander of the U.S. forces in Korea, listens to South Korean Gen. Yun Kong-yong, as he tours artillery-damaged areas on Yeonpyeong Island on Friday. (Jo Yong-Hak/Reuters)

"The U.S. does want to show that any attack against South Korea is an indirect attack against the United States," freelance reporter Jason Strother told CBC News from the island.

In South Korea, President Lee Myung-bak is taking a great deal of political fire for the South's response to the North's artillery attack. Defence minister Kim Tae-young quit, but opposition parties and the local media are asking why the north is allowed to get away with killing four people, and attacking South Korean soil for the first time since the Korean War.

On Friday, the president replaced Kim Tae-young with Kim Kwan-jin, a former chairman of the Joint Chiefs of Staff.

North Korea's state media, in its typically dated but colourful language, denounced the U.S. and South Korea for pushing the Korean Peninsula to the brink of war, CBC's Anthony Germain reported.

Police officers put yellow tape around houses destroyed by North Korean artillery shelling at a village on Yeonpyeong Island on Friday. (Jo Yong-Hak/Reuters)

The North's official Korean Central News Agency warned of another "shower of dreadful fire," and earlier had said "the situation on the Korean peninsula is inching closer to the brink of war."

Tuesday's strike destroyed large parts of Yeonpyeong Island, in a major escalation of the two countries' sporadic skirmishes along the sea border.

The attack came eight months after a torpedo sank a South Korean warship and killed 46 sailors. It also comes during a transition process between leader Kim Jong-il and his inexperienced son Kim Jong-un, who is in his late 20s.

The two Koreas have been under an armistice, not a peace treaty, since the Korean War ended in 1953. North Korea does not recognize the maritime border drawn by the United Nations after the conflict and considers the waters around Yeonpyeong Island North Korean territory.

With files from The Associated Press