North Korea has redeployed troops and equipment at the front-line guard posts within the Demilitarized Zone after withdrawing from a military agreement with South Korea last week.
The North Korean military has been spotted re-installing surveillance posts, according to surveillance footage provided by the South Korean military Monday.
Photos taken by the South Korean Defense Ministry show temporary structures made of wood in eleven locations where they had blown up along the border in accordance with the inter-Korean military agreement signed on September 19, 2018.
"South Korean military is closely monitoring North Korean military's movements at the frontline area and maintaining readiness posture accordingly," South Korea's Defense Ministry spokesperson Jeon Ha-kyu said during a press briefing Monday.
South Korean Joint Chief of Staff Kim Myung-soo pointed out to reporters that it was the North Koreans who withdrew from the implementation of the "9-19 North-South military agreement" and "because it is North Korea that broke the trust, we will take corresponding measures."
The 2018 inter-Korean military agreement included removing guard posts at border areas and buffer and no-fly zones near the armed border. It was signed by then South Korean President Moon Jae-in and North Korean leader Kim Jong Un in 2018 during a brief reconciliatory mood between the two Koreas.
"This typical move by North Korea to ratchet up tensions was widely expected after they announced last week that military measures will be restored," Dr. Cha Du Hyeogn at Asan Institute told ABC News. "North Korea will likely provoke the South Korean military with small-scale gunfires when South Korea carries out its principled response."
Last week, North Korea celebrated putting its own satellite into orbit with help from Russian technology after two failures in the past years.
North Korea claims that its spy satellite, Malligyong-1, is operational and has transmitted images of a U.S. base in Guam and several South Korean key military sites. However officials from South Korea and the U.S. have not confirmed whether it is capable of functioning reconnaissance missions.
This launch, a stride in North Korea's burgeoning space program, marks a significant advance in the nation's military potential, particularly in the realms of space-based recon and rocketry.
Pyongyang has announced that the satellite's official mission will commence in December
ABC News' Anthony Trotter contributed to this report.