An April 15, 2022 photo from the South Korean border city of Paju shows soldiers (top) outside a guard post in North Korea, as seen beyond a South Korean guard post (bottom). AFP-Yonhap

North Korea's military said it will cut off all roads and railways connected to South Korea starting Wednesday and build "strong defense structures" in the areas in response to South Korea-U.S. military maneuvers.

"A project will be launched first on October 9 to completely cut off roads and railways connected to" South Korea and "fortify the relevant areas of our side with strong defense structures," the general staff of the North Korean People's Army said in a report carried by the Korean Central News Agency, noting the measures will "completely separate" North Korea's territory from that of South Korea.

"For our army to permanently shut off and block the southern border with the ROK, the primary hostile state and invariable principal enemy, in the current situation is a self-defensive measure for inhibiting war and defending the security of the DPRK," it said, referring to South and North Korea by the acronyms of their formal names.

North Korea said it was taking a "more resolute and stronger measure" in response to the "acute military situation" on the Korean Peninsula, citing South Korean military exercises staged near the border and visits by U.S. strategic nuclear assets to the region.

North Korea's military said it sent a telephone message to the U.S. military in South Korea at 9:45 a.m. to "prevent any misjudgment and accidental conflict over the fortification project."

The announcement came amid ongoing tensions on the Korean Peninsula as the North has sent trash-carrying balloons toward the South and publicly disclosed a uranium enrichment facility for the first time.

The U.S. stations some 28,000 troops in South Korea to deter North Korean aggression, a legacy of the 1950-53 Korean War that ended in an armistice, not a peace treaty.

South Korea's Joint Chiefs of Staff (JCS) said it had not detected any construction work by the North Korean military near the border as of Wednesday morning.

"Our military will not overlook any action by North Korea attempting to unilaterally change the status quo, and we clearly warn that responsibility for all situations resulting from it lies with North Korea," the JCS said in a statement.

"In the event North Korea carries out a provocation, our military will overwhelmingly punish not only the source of the provocation but also the supporting and commanding forces based on a firm combined defense posture."

The Koreas are connected by road and railway along the Gyeongui line, which connects the South's western border city of Paju to the North's Kaesong, and the Donghae line along the east coast.

Since North Korean leader Kim Jong-un characterized the Koreas as "two hostile states" late last year, the North has taken steps to eliminate routes once seen as symbols of inter-Korean exchange and cooperation, including by installing mines along the Gyeongui and Donghae roads in January. (Yonhap)