North and South Korea exchanged warning shots early Monday morning along a disputed western maritime boundary in the Yellow Sea after a North Korean warship crossed a sea border with the South.

Yonhap News Agency reported that the Joint Chiefs of Staff (JCS) of South Korea fired warning shots after a North Korean merchant vessel breached the Northern Limit Line (NLL) at 3:42 a.m. local time on Monday.

The NLL is the de facto sea border as established by the United Nations Command after the conclusion of the Korean War of 1950-1953.

According to the state-run Korean Central News Agency, North Korea's military later published a statement saying that it fired 10 shells from various rocket launchers at 5.15 a.m. (local time) where "naval enemy movement was spotted" (KCNA).

State media said that the Korean People's Army (KPA) accused the South Korean naval ship of invading North Korea's border by 2.5 to 5 kilometers (1.5 to 3 miles) at approximately 3:50 a.m. under the pretext of "managing an unidentifiable ship."

The KPA stated that warning shots were fired again to deliver a "grave warning" to South Korea over its maritime incursion, referencing its prior artillery fire on the ground front that was intended to warn South Korea after its military exercises on the Korean Peninsula.

The KPA was referring to its artillery fire on October 18, when it launched approximately 100 artillery rounds off its west coast and another 150 rounds off its east coast to warn South Korea.

14 October, in reaction to South Korea's joint military exercises with the United States, North Korea launched 560 rounds into the buffer zone separating the two Koreas. No damages were reported as a result of the incidents.

The Joint Chiefs of Staff stated that North Korea's artillery fire breached their Comprehensive Military Agreement, which called for a suspension of hostilities between the two Koreas, and demanded that North Korea cease its provocations that undermine regional stability.

North Korea has increased its missile launches and despatched jets in retaliation for South Korea's and the United States' joint military exercises on the Korean Peninsula, which it views as an "invasion rehearsal."

The KPA stated that the artillery fire was intended to convey a "severe warning" to South Korea in response to the latter's "frantic war exercise against the North."

In the meantime, the North Korean government has stated that it is prepared to deploy nuclear weapons against "hostile forces" in light of its repeated missile launches.

Last month, North Korea enacted new legislation permitting it to undertake an "automatic" nuclear strike against any "hostile forces" posing an imminent threat. The law, according to North Korean leader Kim Jong Un, will make the nuclear position of his country irrevocable.