Tensions between North Korea and South Korea rose on Monday after the countries' armies exchanged artillery fire along their border on the Yellow Sea.
The North Korean army fired about 500 artillery rounds during live-fire exercises, with about 100 shells falling in South Korean waters, the South Korean Defense Ministry said.
South Korea's navy responded by firing several dozen rounds from K-9 howitzers into North Korean waters.
South Korean air force F-15s patrolled the area and residents of islands in the Yellow Sea near North Korea's border were evacuated, officials said.
North Korea has deployed about 1,000 artillery pieces and other weapons along its southwest coast, South Korean officials said.
China, North Korea's strongest ally and biggest trading partner, urged Pyongyang and Seoul to "act with moderation, avoid measures that could raise tensions and make joint efforts to maintain peace and stability."
Tensions have been running high on the Korean peninsula since late February, when South Korea and the United States began military exercises.
Some 7,500 U.S. personnel are participating in the military exercises, which end on April 28.
North Korea contends the exercises are a "rehearsal for an invasion" of its territory and has responded by firing short-range and medium-range missiles.
South Korea and North Korea are still technically at war because the 1950-1953 Korean War ended with an armistice rather than a peace treaty. EFE