South Korea returned fire into North Korean waters on Monday after shells from a North Korean live-fire drill fell south of the rivals' disputed western sea boundary, a South Korean military official said, according to CNN.
No shells from either side were fired at any land or military installations, an official with South Korea's Joint Chiefs of Staff who spoke on conditions of anonymity said, CNN reported.
The exchange of fire followed Pyongyang's earlier, unusual announcement that it would conduct the live-fire drills, a move seen as an expression of Pyongyang's frustration at making little progress in its recent push to win outside aid, according to CNN.
In recent weeks, North Korea has increased threatening rhetoric and conducted a series of rocket and ballistic missile launches that are considered acts of protest against annual ongoing springtime military exercises by Seoul and Washington, CNN reported.
The North calls the South Korea-U.S. drills a rehearsal for invasion; the allies say they're routine and defensive, according to CNN.
After the North's earlier announcement on Monday that it would conduct firing drills in seven areas north of the sea boundary, South Korea responded that it would strongly react if provoked, CNN reported.
Wee Yong-sub, a deputy spokesman at the South Korean Defense Ministry, said the North Korean message was a "hostile" attempt to heighten tension on the Korean Peninsula, according to CNN.
In 2010, North Korea launched artillery strikes on a front-line South Korean island near the boundary, killing four, in response to a drill by South Korea earlier in the day, CNN reported.
The North has since gradually dialed down its threats and sought improved ties with South Korea in what foreign analysts say is an attempt to lure international investment and aid, according to CNN.
The Korean Peninsula remains in a technical state of war because the 1950-53 Korean War ended with an armistice, not a peace treaty, CNN reported. About 28,500 American troops are deployed in South Korea to deter potential aggression from North Korea.
