Ten North Korea soldiers' bungled journey over the South's border - into a zone with 2m mines

South Korean troops opened fire with warning shots earlier today after bungling troops from the North crossed the rivals' tense and heavily-armed border. The dramatic escalation on the heavily militarised border was the first known intrusion by North Korea in nearly a year and comes at a tense time for Seoul.

Violent confrontations and bloodshed have occasionally happened at the Koreas' heavily fortified border, called the Demilitarized Zone. But no casualties on either side were caused and North Korea has not returned fire. Ten North Korean soldiers - some carrying weapons - violated the military demarcation line at the eastern section of the famous DMZ separating the two Koreas at 5pm. They returned to North Korea after South Korea broadcast warnings and fired warning shots, South Korea's Joint Chiefs of Staff said.

South Korean and US troops are on permanent alert for another attempted incursion and Seoul’s military is closely monitoring North Korean activities. In June last year, North Korean troops violated the border three times, prompting South Korea to fire warning shots.

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The incidents occurred when the Koreas were embroiled in Cold War-style campaigns like balloon launches and insulting propaganda broadcasts. North Korea’s balloon launches often carried rubbish and messages insulting the south.

South Korea's military believes the North Korean soldiers mistakenly made the border intrusion and the site of the error was a wooded area where military demarcation line signs were not clearly visible. Observers said the North Korean soldiers might have accidentally crossed the border while adding anti-tank barriers, planting mines or engaging in other works to boost border defences.

South Korea's military said in late March that North Korea was resuming front-line works such as reinforcing barbed wire fences. Seoul's media suggested North Korean soldiers might have unintentionally intruded into South Korea's territory on Tuesday during a patrol mission.

In October, North Korea said it would build defence structures at the border to cope with "confrontational hysteria" by South Korean and US forces. That was seen as an effort to beef up its front-line security posture and prevent its soldiers and citizens from defecting to South Korea.

The 155-mile long and 2.5-mile-wide DMZ is one of the world's most heavily armed borders. Two 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 1950-53 Korean War, which ended with an armistice, not a peace treaty. Animosities between the Koreas are running high now as North Korean leader Kim Jong Un continues to flaunt his military nuclear capabilities and align with over President Vladimir Putin's war on .

Kim is also ignoring calls by Seoul and Washington to resume denuclearisation negotiations. Since his Jan. 20 inauguration, U.S. President has said he would reach out to Kim again to revive diplomacy. North Korea has not responded to Trump's remarks and says U.S. hostilities against it have deepened since Trump's inauguration.

Experts say Kim could eventually return to talks with Trump, hoping that his advancing nuclear program would help North Korea win greater U.S. concessions. South Korea, meanwhile, is experiencing a leadership vacuum after its President Yoon Suk Yeol was sacked last week over his ill-fated imposition of martial law. Yoon's push to expand military drills with the US had infuriated North Korea.