SEOUL: Pyongyang has accused Seoul of sending warships into its waters off the peninsula's west coast, warning of a naval clash.

Pyongyang does not recognize the sea boundary off the divided peninsula's west coast. The DPRK claims that the United Nations unilaterally drew the line at the end of the 1950-53 Korean War, and that it should be redrawn further south.

The dispute led to two naval skirmishes in 1999 and in 2002.

But the latest warning came as relations between the two Koreas showed signs of improvement with the DPRK taking a series of conciliatory steps like freeing detained ROK citizens and pledging to resume stalled joint projects.

On Wednesday, the DPRK offered a rare apology to the ROK for releasing a massive amount of water from a dam that sparked flooding blamed for six ROK deaths.

Ties between the two sides had badly frayed as Pyongyang cut off reconciliation talks and suspended joint projects in anger over the hard-line policy that Seoul's conservative President Lee Myung-bak has taken toward the DPRK since taking office last year.

The two Koreas fought the 1950-53 Korean War, which ended in a truce, not a peace treaty, which means that the sides are still technically at war.