South Korea proposed talks with North Korea on Monday to ease military tensions, the first such offer in seven years as Seoul seeks to ease military tensions with the nuclear-armed North.

South Korea's military says it has been firing warning shots to repel North Korean troops who violated the border's military demarcation line numerous times since they began engaging in work to boost front-line defences last year.

Kim Hong-cheol, deputy minister for national defence policy, told a news briefing that military-to-military channels can help avert an escalation.

North Korea has denied that and threatened unspecified responses, saying its soldiers worked within the North's territory.

South Korean officials said that the North's border intrusions were likely caused by the rival's different views on the border line, because many of the military demarcation line posts established at the end of the 1950-53 Korean War have been lost due to maintenance being suspended for more than 50 years.

The proposed military talks follow South Korean President Lee Jae Myung's offer of broader discussions with the North without preconditions, a sharp reversal from the hawkish stance taken by his conservative predecessor. North Korea has yet to respond to Lee's overtures.

If it accepts the latest proposal, it will mark the first military talks between the two sides since 2018.

Last year, North Korean leader Kim Jong Un declared that his country was abandoning its long-standing goals of a peaceful unification between the Koreas and ordered the rewriting of the North's constitution to mark the South as a permanent enemy.

South Korea's military said that it has since detected North Korea adding anti-tank barriers and planting more mines at border areas.

The Koreas' 248-kilometre-long, four-kilometre-wide border is one of the world's most heavily armed frontiers. An estimated 2 million mines are peppered inside and near the border, which is also guarded by barbed-wire fences, tank traps and combat troops on both sides. It's a legacy of the Korean War, which ended with an armistice, not a peace treaty. (AP, AFP)