The two Koreas exchanged “warning shots” off the western coast after a North Korean merchant vessel “intruded” over the de facto inter-Korean maritime boundary and crossed into South Korean waters early Monday morning.

North Korea’s border intrusion came hours before South Korea and the United States began staging their four-day large-scale maritime maneuvering exercise in the West Sea to enhance combined and joint operational capabilities against “enemy provocations.”

A North Korean cargo ship, identified as Mupho-ho, “intruded across the Northern Limit Line” at 3:42 a.m. on Monday, South Korea’s Joint Chiefs of Staff confirmed on the day. The NLL is the de facto, but disputed, inter-Korean maritime boundary.

The merchant ship crossed the inter-Korean maritime border around 27 kilometers northwest of the island of Baengnyeongdo.

The South Korean military “broadcast warnings and fired warning shots” to repel the North Korean ship.

Monday’s border intrusion marks the first time that a North Korean merchant ship has breached the NLL since January 2017, according to the South Korean military.

The North Korean vessel traveled around 3.3 km south of the NLL and stayed in South Korean waters for around 40 minutes, South Korean military officials -- who wished to remain anonymous -- confirmed Monday morning during a closed-door briefing.

The vessel crossed the NLL to turn back toward North Korean waters at around 4:20 a.m. and headed toward China. The South Korean military identified the Mupho-ho ship as a 5,000-ton bulk carrier.

The South Korean military broadcast warnings around 20 times before and after the North Korean ship trespassed into South Korean waters, but the merchant ship did not turn around.

Then, the South Korean military fired around 20 warning shots with M60 machine guns in two discrete firings to see off the North Korean vessel, unnamed South Korean military officials confirmed. The M60 machine guns are not in violation of the Sept. 19 inter-Korean military agreement.

The South Korean military dispatched several vessels, including a frigate, as well as joint forces in response to North Korea’s border intrusion.

The South Korean vessels were around 1 km from the North Korean merchant ship. The North Korean ship also warned South Korean vessels not to cross into North Korean waters by sending messages several times.

Tit-for-tat near inter-Korean borders
In response to South Korea’s warning shots, the North Korean military fired around 10 artillery shells off the western coast from Jangsan Cape in South Hwanghae Province at 5:14 a.m., according to South Korea’s JCS. The artillery firing came less than an hour after the North Korean merchant ship retreated into North Korea waters.

Monday’s military action is in line with North Korea’s recent move to continue to fire artillery shells into inter-Korean maritime buffer zones, while justifying the barrages as countermeasures against annual military exercises between South Korea and the United States.

The artillery shots also fell inside inter-Korean maritime buffer zones on Monday morning, but north of the NLL, the JCS added. The two Koreas agreed to cease all live-fire and maritime maneuver exercises in the buffer zones in a military tension reduction deal signed during an inter-Korean summit on Sept. 19, 2018.

“It is a clear violation of the Sept. 19 military agreement and provocation that the North Korean military fired shells from multiple rocket launchers in response to the South Korean military’s normal operational measures against the North Korean merchant vessel intruding over the NLL,” the JCS said in a statement.

An unnamed spokesman for the North's General Staff of the Korean People’s Army said the military “opened 10 threatening and warning fires in the direction of 270 degrees of firing azimuth from the area of Ryongyon County at 5:15 (a.m.) on October 24” in an English-language statement. The statement was issued Monday morning immediately after North Korea took the military action.

The KPA General Staff claimed that the North Korean military fired warning shots after the South Korean Navy’s frigate intruded across the maritime military demarcation line designated by North Korea in the waters 20 km northwest of Baengnyeongdo at around 3:50 a.m.

The KPA General Staff argued that the South Korean escort ship “invaded” the North Korea-designated maritime border by 2.5 to 5 km with the excuse of clamping down on an unidentified vessel.

North Korea does not recognize the NLL and claims its own inter-Korean maritime military demarcation line, which is designated several kilometers south of the NLL.

“The KPA General Staff once again sends a grave warning to the enemies who made even naval intrusion in the wake of such provocations as the recent artillery firing and loudspeaker broadcasting on the ground front,” the statement read, without further details.

But the South Korean military officials on Monday refuted, saying it has suspended loudspeaker broadcasting. The Moon Jae-in government announced that it would halt anti-North Korean propaganda broadcasts using loudspeakers near the inter-Korean border on April 23, 2018, in the run-up to the inter-Korean summit.

The South Korean military explained that it recently delivered a message publicly to North Korea through broadcasting equipment installed at front-line guard posts. But the broadcast aimed to let North Korea know that a South Korean helicopter entered an area north of the Civilian Control Line to transport an emergency patient.

Calculated move?
The North Korean vessel’s intrusion across the inter-Korean military demarcation line came hours before the South Korean and US army, navy and air forces and the South Korean Coast Guard kicked off large-scale combined exercises on Monday morning in the West Sea.

The four-day combined maritime training exercises are part of the South Korean military-led major Hoguk field training exercise that continues until Friday, the South Korean Navy announced Monday.

The combined exercises aim to “improve capabilities to carry out combined and joint naval operations in preparation for enemy provocations” and interoperability between the South Korean and US forces, according to the South Korean Navy

The South Korean Navy explained that the South Korean and US forces also seek to “maintain the highest state of military readiness through intensive training exercises,” underscoring that the exercises are defensive in nature.

The major training exercises practice maritime counter-special operations and maritime interdiction operations and master operational procedures in real-world scenarios, including North Korea’s local provocations along the NLL.