BEIJING/SEOUL - North Korea has denied involvement in mine blasts last week that injured three South Korean soldiers in the Demilitarized Zone dividing the Korean Peninsula, saying Seoul should pay the price for a "farce of their own making," state-run media said Wednesday.

Kim Yo Jong, the influential younger sister of North Korean leader Kim Jong Un, said in a statement Tuesday the country's soldiers "have never crossed the border" and warned that Pyongyang would retaliate if South Korean forces open fire at its troops in the border area, according to the official Korean Central News Agency.

Her statement came after the South Korean military said in a preliminary assessment Monday that North Korea had likely planted mines on the southern side of the DMZ that exploded on Sept. 21. Seoul has warned it would take corresponding measures if final findings confirm the mines had been laid by North Korea.

South Korea's military on Wednesday urged North Korea to issue an apology and take responsible measures for the injuries the blasts have caused.

Seoul claimed that Pyongyang's "border fortification," such as laying mines near the military demarcation line, and all other activities that escalate tensions on the Korean Peninsula must be halted.

Kim Yo Jong, who also serves as a senior official of the ruling Workers' Party of Korea, accused South Korea of "cooking up the groundless results" and "justifying their conduct for political and military provocation" against North Korea.

"Our army has been building the barriers in the southern border area as part of the work of strengthening the border two years ago, and this is only a thorough exercise of sovereignty unrelated with any military purpose," she said.

If the South Korean military fires at North Korean soldiers, "our border units will take immediate and merciless retaliate attack," she added.

South Korea's National Intelligence Service assessed Kim Yo Jong's statement to be low key in terms of its tone during the agency's briefing with the intelligence committee at the parliament on Wednesday.

"The NIS analysis found that the main thrust of Kim Yo Jong's statement was to dismiss the incident as a fabrication and to deny any connection to North Korea," ruling Democratic Party lawmaker Youn Kun Young told reporters after the briefing.

Similar land mine explosions occurred near the military demarcation line in 2015, raising tensions between the two Koreas.

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