North Korean leader Kim Jong-un (center) points to a spot on a large map during his inspection of the 2nd Corps of the Korean People's Army on Thursday in this photo released by the North's official Korean Central News Agency(KCNA) the following day. (Yonhap)

North Korean leader Kim Jong-un has referred to South Korea as "a foreign country and an apparent hostile country," warning that physical force will be used if the North's sovereignty is violated, state media reported Friday.

The remarks were made during his inspection of the headquarters of the 2nd Corps of the Korean People's Army on Thursday, two days after Pyongyang blew up roads and railways connected to South Korea that were once considered key symbols of inter-Korean reconciliation.

"He stressed that our army should keep in mind once again the stark fact that the ROK is a foreign country and an apparent hostile country," the Korean Central News Agency said in an English-language dispatch.

ROK stands for South Korea's official name, the Republic of Korea.

It is widely speculated that Pyongyang has recently amended its constitution to define Seoul as a hostile state to align with Kim's directive to formally designate the South as an enemy, rather than a partner for reconciliation and reunification.

"And he added that it also means the last declaration that when the DPRK's sovereignty is violated by the ROK, a hostile country, its physical forces will be used unhesitatingly, without sticking to conditions any longer," the KCNA said.

DPRK stands for the North's official name, the Democratic People's Republic of Korea.

Kim said that blocking roads and railways not only means the physical closure but also the end of the evil relationship with Seoul and the complete removal of the unreasonable idea of reunification.

During the inspection, Kim again cited the importance of bolstering the war-fighting capability and defending the security of the country through the permanent overwhelming combat readiness, including nuclear deterrence.

"The impact of the changed nature of the ROK-US alliance and the more developed different enemy military maneuvers of aggressive nature on the DPRK's security more clearly highlights the importance of strengthening its nuclear deterrent and proves its validity," Kim said.

Photos released by the KCNA show Kim pointing to a large map on a table, mostly blurred but revealing Seoul, indicating that the 2nd Corps of the Korean People's Army may have formulated an attack plan targeting the South Korean capital.

The photos also show a large TV screen behind Kim displaying a map of the Korean Peninsula, with a thick blue line drawn in a location close to the Demilitarized Zone separating the two Koreas.

Kim was accompanied on his field inspection by Pak Jong-chon, vice chairman of the Central Military Commission of North Korea's ruling Workers' Party, and No Kwang-chol, minister of National Defence of the DPRK. (Yonhap)