Pyongyang, North Korea - North Korea has sent troops to its southern border to restore guard posts taken down under a 2018 agreement with South Korea, Seoul's military said Monday, after Pyongyang's launch of a spy satellite stoked tensions on the peninsula.

In response to the launch last week, Seoul partially suspended the agreement that was aimed at easing border tensions, prompting Pyongyang to scrap the pact entirely and warn it would "never be bound" by the deal again.

A military official told AFP on Monday that Pyongyang had recently sent armed personnel and equipment to restore the guard posts.

Yonhap news agency reported that North Korean soldiers were "seen rebuilding the guard posts from Friday," according to a military official, and that all 11 posts withdrawn under the five-year-old military accord were expected to be restored.

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One photo released by South Korea's military shows four North Korean soldiers rebuilding a wooden guard post in the Demilitarized Zone that separates the two countries.

North Korea's accelerated development of its weapons programs has alarmed Seoul.

South Korea deployed "surveillance and reconnaissance assets" to the border after the satellite launch, in what its military said was an "essential measure" to defend against nuclear-armed North Korea's growing threats.

In response, Pyongyang said it would "deploy more powerful armed forces and new-type military hardware in the region along the Military Demarcation Line" between the two Koreas.

Last week's launch of the Malligyong-1 was Pyongyang's third attempt at securing a military eye in the sky after two failures in May and August.

Successfully putting a spy satellite into orbit would improve North Korea's intelligence-gathering capabilities, particularly over South Korea, and provide crucial data in any military conflict, experts say.