North Korea has started to restore guard posts within the demilitarized zone, which had previously been demolished in accordance with the 2018 inter-Korean military agreement, while bringing military personnel and firearm equipment back to the posts, Seoul said Monday.

Movements to restore the military posts have been detected since Nov. 24, one day after North Korea declared a complete annulment of the Sept. 19 military agreement, the Defense Ministry in Seoul said in a statement.

South Korea's Defense Ministry also released photos captured by ground-based surveillance equipment, including thermal observation devices, that show the activities of the North Korean military in the eastern region near the inter-Korean border.

Seoul has observed that Pyongyang has deployed its military personnel and heavy firearms, and is constructing observation posts atop of formerly demolished guard posts, in an apparent attempt to restore the 11 guard posts.

In 2018, as part of the Sept. 18 Comprehensive Military Agreement, South and North Korea Korea had dismantled 10 guard posts located within 1 kilometer of each other in the DMZ, covering the eastern, western and midland regions. While one guard post, acknowledged for its historical significance, was preserved from each side, the withdrawal of all military personnel and equipment from the guard posts took place.

"There have been sporadic military activities at certain previously destroyed guard posts (since 2018). However, activities such as the construction of observation posts, importing heavy firearms or engaging in continuous day and night border surveillance, as is currently being observed, had not been observed," a senior military official told reporters on condition of anonymity.

The images depict North Korean soldiers constructing an observation post atop the previously demolished guard post using wood. Additionally, they show the soldiers applying camouflage patterns to the observation post.