South Korea's military said Monday it fired warning shots at a North Korean ship that crossed the de facto border of the two countries, prompting North Korea to fire warning shots in return.

Pyongyang has conducted a series of weapons tests, including what it says were tactical nuclear exercises, in recent weeks, while Seoul and Washington have stepped up joint military exercises in response.

With talks stalled for a long time, relations between North and South Korea are at their lowest point in years with Kim Jong Un declaring last month that Pyongyang's status as a nuclear power was "irreversible", ending negotiations over its banned weapons programmes.

The maritime boundary, which was not formally defined in the 1953 agreement that ended hostilities in the Korean War, remains a hotspot and has been the scene of numerous inter-Korean clashes over the years.

The South Korean Joint Chiefs of Staff said that a North Korean merchant ship crossed the so-called Northern Limit Line near Pingnyeong Island at 3:42 a.m., but retreated north after the South Korean navy fired warning shots.

"North Korea's continued provocations and irresponsible actions undermine peace and stability on the Korean peninsula and the international community," the agency said in a statement, urging Pyongyang to "stop it immediately."

- North Korea's response -

For its part, the North Korean army said that a South Korean military ship violated the de facto border of 2.5 to 5 kilometers minutes after the first incident, prompting the People's Army to fire 10 warning shots at it in response.

"Coastal defense units of the Korean People's Army on the western front... took an initial countermeasure to expel an enemy warship by firing 10 rounds of missile launchers towards the territorial waters, where they detected sea movement," a North Korean military spokesman said in a statement carried by state media. hostile at 5:15.

"We once again strongly warned the enemies who carried out naval provocations in addition to artillery fire and loudspeaker broadcasts across the border," he added.

North Korea fired several artillery shells this month into the maritime "buffer zone" established in 2018 to reduce tension between the two countries during a period when all diplomatic efforts failed.

These moves are part of what Seoul considers "provocations" by North Korea, including the launch of a medium-range ballistic missile that flew over Japan and raised rare evacuation warnings, a precedent since 2017.

Also, Seoul recently conducted live-fire exercises while the United States redeployed a nuclear-powered aircraft carrier to the region for large-scale trilateral exercises that also included Tokyo.

"The incursion of the ship and North Korean artillery fire show that there is no consensus on the limits of the NLL," Cheong Seong-chang, a researcher at the Sejong Institute, told AFP.

"North Korea may try to neutralize the NLL at a later time given the background of military confidence in its tactical nuclear arsenal," he explained.

Pyongyang has stepped up its military exercises significantly recently, while Seoul and Washington have said that North Korean leader Kim Jong Un is about to conduct what could be his country's seventh nuclear test.

Kim has made the development of tactical nuclear weapons, which are smaller, battle-ready weapons, a priority while Seoul recently warned that North Korea may prepare for successive nuclear tests as part of that.

Monday's warning fire came on the same day that US Deputy Secretary of State Wendy Sherman visits Japan and holds three-way talks with Japan and South Korea, in a show of unity after a series of missile launches from North Korea.

Source: AFP