The South Korean joint forces said Thursday a patrol boat of the Democratic People's Republic of Korea (DPRK) intruded the S. Korean side of the West Sea, and retreated after nearly an hour, following warning signals of a S. Korea's high-speed vessel, South Korea's Yonhap News Agency reported.

The boat, crossing the border at around local time 2:47 p.m. ( 0547 GMT), headed back to its territory at 3:38 p.m. (0638 GMT) as a South Korean naval vessel sounded warning signals, a Joint Chief of Staff official was quoted as saying by Yonhap in Seoul.

The Korean Peninsula has been amid heightened tension as the DPRK warned last week against the safety of South Korean vessels operating near South Korea's Northern Limit Line (NLL) located in the West Sea.

The DPRK has been claiming that the NLL, originally set by a U. S. commander at the end of the Korean War, should be drawn further south.

(Xinhua News Agency June 4, 2009)