North Korea-South Korea tensions high as letters lodged with UN, howitzer spotted

South Korea's Yonhap news agency on ​Sunday identified the weapon as a self-propelled 122-mm howitzer, saying its deployment near the border marked a rare public display of such artillery.

Reuters ​also observed three North Korean armored vehicles with their gun barrels pointed south, as well as about 20 to ⁠30 North Korean soldiers carrying out fencing work inside the Demilitarised Zone (DMZ). "It is highly unusual (for North Korea) to expose its self-propelled artillery so conspicuously,” said ​Lim Eul-chul, a professor at Kyungnam University in Seoul.

"By deliberately displaying it, North Korea is signalling through action, not words, that it intends to enforce its ​border policy through force rather than dialogue or negotiation. "It is also warning South Korea to exercise caution about escalating border friction, with the intention to prevent an accidental clash, he added.

North Korean state media KCNA reported that in the letter sent on Sunday, the country's UN representative said Seoul was using the landmine incident to depict Pyongyang's border ​construction as a military incursion.

North Korea warned in the letter that violations of its sovereignty could trigger self-defence measures and that South Korea would be "wholly ​accountable for all the ensuing consequences.

"PHOTOS ALSO SHOW NORTH KOREAN DRILLSThe letter is a response to a South Korean letter to the Security Council last week, which said a ‌September 21 ⁠blast in the DMZ was planted by North Korean troops and constituted a violation of the Korean War Armistice Agreement.

The UN Command, which oversees the DMZ, has said a North Korean mine across the line violated the armistice. Pyongyang has denied responsibility. A spokesperson for South Korea's Unification Ministry said on Monday that the North Korean letter appears to repeat North Korea's existing position and seeks to justify its so-called border line marking work.

The ministry had no separate ​comment on the placement of the howitzer. ​Seoul has proposed dialogue with North ⁠Korea to defuse border tensions. North Korea's letter also repeated accusations that South Korea had opened fire on North Korean personnel, calling that a violation of the UN Charter, which bars the threat or use of force against another state's ​territorial integrity.

Seoul has said its military issues warning broadcasts and fires warning shots to send North Korean soldiers ​back across the line ⁠when they cross the military demarcation line (MDL), which bisects the DMZ.North Korean troops have been building tactical roads and fences and laying mines near the MDL in recent years.

The Yonhap report cited photographs taken from an observatory in the South Korean border city of Gimpo that appeared to show the howitzer as well as ⁠North Korean ​troops conducting drills on the coast of Kaepung county, about 1.5 km (1 mile) from the ​observatory.

In 2015, there was a similar incident in which South Korean troops were injured by North Korean mines. Then, Seoul resumed anti-North Korea loudspeaker broadcasts across the DMZ, triggering a military standoff. ​After North Korea expressed regret, the standoff ended with a high-level inter-Korean agreement.