SEOUL - A patrol ship of the Democratic People's Republic of Korea (DPRK) was sent back Tuesday after "violating South Korea's territorial waters", the Joint Chiefs of Staff said.

The patrol boat sailed about 1.5 km south of the Northern Limit Line (NLL), which the DPRK has never accepted as the inter-Korean maritime border as it was unilaterally drawn by the United Nations after the 1950-1953 Korean War.

The ship came back after sailing in waters near the western border island of Yeonpyeong at around 10:22 am (0122 GMT).

The South Korean Navy issued warning messages and fired warning shots to force the ship back to the north.