One artillery round was heard from a North Korean military base north of the sea border dividing the two Koreas, an official with South Korea’s Joint Chiefs of Staff said. He spoke on condition of anonymity, citing office rules.

Residents of Yeonpyeong Island were ordered to take shelter because of the sound, he said. The evacuation order was later lifted.

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.

The artillery sound and the evacuation came just hours after South Korea and the United States launched joint military drills near the area.

The exercises came as the North worked to justify one of the worst assaults on South Korean territory since the 1950-53 Korean War.

North Korea said civilians were used as a "human shield" around artillery positions and lashed out at what it called a "propaganda campaign" against Pyongyang.

It claimed the United States orchestrated last Tuesday’s clash so that it could stage joint naval exercises in the Yellow Sea with the South that include a U.S. nuclear powered supercarrier — enraging the North and making neighboring China uneasy.

Also Sunday, a Chinese State Councilor Dai Bingguo met with South Korean President Lee Myung-bak in Seoul, according to Lee’s office, which provided no details. South Korea’s Yonhap news agency said they discussed the North Korean attack and how to ease tensions.