This is the first exchange of accusations since the two navies established a direct wireless communication system between warships in June. Pyongyang’s claims are seen as psychological warfare aimed at undermining the integrity of the NLL, but the Southern Navy says it is prepared for possible North Korean provocations.

"We express serious concern over repeated claims by North Korea's naval command that our warships conducting routine patrols have violated North Korea's territorial waters," Navy headquarters said Friday. “We are scrutinizing North Korean intentions, and we are completely ready for any potential situation."

It warned the North that “responsibility for this incident rests entirely with the North Korean Navy, and we demand that it stop making distorted claims that could raise the level of tensions in the waters along the current maritime border."

North Korean naval command claimed on Jan. 21, 24 and 27 that South Korean naval vessels were raising tensions by "nakedly" violating the North’s territorial waters in the West Sea.

A spokesperson for North Korean naval command said, "The South Korean Navy is justifying its violations of our waters through its media and has openly revealed its intention to stubbornly maintain the bogus 'Northern Limit Line', which was drawn by outside powers."

South Korean military authorities plan to explain Seoul's position through intra-Korean communication channels to avoid a repeat of clashes in the waters along the NLL.

(Yu Yong-won, bemil@chosun.com )