Dozens of North Korean soldiers briefly crossed the heavily fortified border with the South on Tuesday and retreated after warning shots were fired, South Korea's military said.
The military added that landmine explosions had injured North Korean troops in the area, however it did not reveal the date of these incidents.
The background: This is the second such incident involving North Korean troops in two weeks, with South Korea's joint chiefs of staff saying they believed the Tuesday crossing — like a previous one on 9 June — was accidental.
On 9 June, the South Korean government said about 20 North Korean soldiers briefly crossed the line that separates the two countries, saying it happened in an overgrown area of the heavily fortified border and was likely accidental.
This year, North Korea has been working to remove streetlights from roads and dig up railway tracks that connected the two countries. Seoul's joint chiefs of staff said that the North Koreans were working on creating "barren land" and laying mines along the border but ended up "suffering multiple casualties from repeated landmine explosion incidents during their work".
The key quote: "North Korea's activities seem to be a measure to strengthen internal control, such as blocking North Korean troops and North Koreans from defecting to the South." — South Korea's joint chiefs of staff.
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What else to know: In recent weeks, North Korea has sent more than a thousand balloons laden with trash, including cigarette butts and toilet paper southward — a response, it says, to balloons carrying anti-Pyongyang propaganda sent north by activists.
In response, the South Korean government has suspended a 2018 tension-reducing military deal and restarted loudspeaker propaganda broadcasts along the border, infuriating the North, which warned Seoul was creating "a new crisis".
What happens now: Tuesday's incident comes as North Korea prepares to receive Russian President Vladimir Putin for a rare state visit likely to boost defence ties between the two isolated countries.
