South Korea’s military has announced that between 20 and 30 North Korean soldiers crossed the inter-Korean border early Tuesday morning. The soldiers returned after South Korean forces fired warning shots.

The event occurred around 8:30am (23:30 GMT on Monday) in the central part of the Demilitarized Zone (DMZ) when the North Korean soldiers crossed the military demarcation line, according to Yonhap news agency, citing the Joint Chiefs of Staff (JCS).

The JCS reported that the North Korean soldiers withdrew quickly once South Korean forces used warning shots. They believe the incursion was not intentional. A similar incident happened just over a week ago in the same area of the DMZ.

The South Korean military also noted that some North Korean soldiers have been injured or killed by landmines in the border region, though the timing of these incidents was not specified. The DMZ and the line of control on the Korean Peninsula are known to be among the world's most fortified and mined borders.

"Several casualties are happening due to multiple landmine detonations in the frontline zone," the JCS stated to the media.

In November, North Korea announced its abandonment of a 2018 military agreement with Seoul, enhancing troop presence and equipment at the border following South Korea’s suspension of parts of the pact. This reaction came after North Korea successfully launched its first military spy satellite.

There has been a notable increase in activity in the region, with the JCS describing that North Korea is dismantling streetlights and railway tracks, installing antitank barriers, and planting mines to create "treeless ground to boost security capabilities".

This latest border incident occurs as North Korean leader Kim Jong Un readies himself to host Russian President Vladimir Putin in Pyongyang, signaling deepening ties between the two nations.

In a message published in the Rodong Sinmun newspaper, the official publication of North Korea’s ruling Workers’ Party, Putin emphasized the strong relations and partnerships that have developed over the last 70 years between the two countries.

"We will build alternative trade mechanisms and mutual settlements free from Western control, and together fight against illegitimate unilateral sanctions," Putin wrote. "Additionally, we will create a framework for equal and indivisible security in Eurasia.”

Putin and Kim previously met in eastern Russia last September.