North Korea is restoring previously dismantled border guard posts amid heightened tensions in the region following the country’s recent spy satellite launch.

South Korea’s Defense Ministry said Monday it discovered North Korea building guard posts at border sites and deploying troops and heavy weaponry, the Yonhap News Agency reported. The news agency said ministry officials shared photos of North Korea troops installing the guard posts.

Under a 2018 agreement, the two Koreas dismantled or disarmed 11 guard posts located inside the heavily guarded border, known as the Demilitarized Zone (DMZ). The agreement also created a no-fly zone at the border and a ban on aerial reconnaissance and live-fire exercises.

The deal, which left South Korea with 50 guard posts and North Korea with 150, was intended to curb front-line military confrontation, though it could be at risk following North Korea’s spy satellite launch last week.

North Korea launched the reconnaissance satellite, called the Malligyong-1, atop a Chollima-1 rocket from the country’s main launch center last week, according to state-run news agency Korean Central News Agency (KCNA). Pyongyang claimed the launch was successful after previous failed attempts earlier this year.

Last week, South Korea’s parliament voted to suspend the 2018 military reduction agreement in the wake of the launch, allowing for restored surveillance activities at the DMZ.

South Korea reportedly said the suspension was “a minimum defensive measure,” since the launch showed the North’s strengthened monitoring of the South and intention to improve missiles.

North Korea railed against the suspension, claiming it would put weapons at the border and will not follow the 2018 deal.

While North Korea has advanced its nuclear and missile capabilities in recent years, it had not, until last week, deployed any major capabilities in space. In May, North Korea’s first launch failed after the rocket fell into the ocean, and a second attempt in August failed due to a technical issue.

North Korea’s national space agency said the space launch was justified because the U.S. and its allies have already militarized space. Both the U.S. and Japan condemned last week’s launch.