A TV screen shows a news report at Seoul Station, Seoul, Monday, about a statement by Kim Yo-jong, the sister of North Korean leader Kim Jong-un, warning of a "horrible disaster" in response to South Korea's alleged drone incursion. EPA-Yonhap

Tensions on the Korean Peninsula have intensified sharply after North Korea ordered its artillery units near the border to be fully prepared to open fire, citing alleged threats from South Korean drone incursions, according to military officials, Monday.

North Korea has accused South Korean drones of dropping anti-Pyongyang leaflets over its capital on three separate occasions earlier this month, a claim that the South Korean military has stated it cannot verify.

According to the North's state-run Korean Central News Agency (KCNA), North Korea's artillery units along the border were ordered late Sunday to be fully prepared to open fire.

"The General Staff of the Korean People's Army issued a directive on Oct. 12, instructing artillery combined units and other key units along the border to prepare for immediate fire," a spokesperson for North Korea's Ministry of National Defense said in a statement.

The directive instructed eight artillery brigades to be ready in accordance with wartime operational protocols by 8 p.m. on Sunday, the KCNA said.

North Korea stated that the move was in response to "a high possibility of additional intrusions" by South Korean drones and warned that such a situation requires an immediate strike. The statement also suggested that the situation could escalate into a broader armed conflict.

In response, South Korea's Joint Chiefs of Staff (JCS) said Monday that it is closely monitoring North Korean military movements and is fully prepared for potential provocations.

"The root cause of these tensions is North Korea. We strongly urge them to cease their vulgar actions, such as launching balloons filled with trash," JCS spokesperson Col. Lee Sung-jun said during a briefing.

Lee said North Korea might be preparing for small-scale provocations, the launch of a military satellite or severing roads along the Donghae and Gyeongui rail lines as a show of force.

Earlier in the day, the South Korean military detected a barricade set up near the railways, which could be interpreted as a last-minute preparation to block access to the roads. This development follows North Korea's announcement on Wednesday to completely sever all roads and railways linked to South Korea and to strengthen its border.

In response to Pyongyang's potential provocations, Lee stated that the military would "strongly retaliate" in self-defense.

However, he remained tight-lipped about North Korea's drone incursion claim, including whether it actually took place or the origin of its launch, maintaining that the military cannot confirm the North's assertions.

A North Korean military guard post, top, and a South Korean post, bottom, are seen from Paju, Gyeonggi Province, near the inter-Korean border, Thursday. AP-Yonhap

"The enemies have their own intentions behind making such public claims, but our goal is to avoid being misled by them. Additionally, if we confirm or disclose any details about the drone's route, it could lead to internal conflicts here," the spokesperson said.

The Ministry of Unification echoed a similar stance regarding the drones, stating that it would not be swayed by North Korea's allegations.

"North Korea has repeatedly fabricated and exaggerated external crises to consolidate its vulnerable regime and control its people. This sudden drone incident appears to have a similar purpose," ministry spokesperson Goo Byung-sam said during a briefing.

"Also, the North may be trying to justify future provocations or incite anxiety and confusion within our society. Regardless of its intentions, North Korea will not achieve its goals through threats and provocations."

Opposition lawmakers have criticized the government's ambiguous stance on the drone incident, arguing that its "neither confirm nor deny" approach fails to alleviate public anxiety regarding the unstable situation.

The main opposition Democratic Party of Korea said Monday it would launch an internal review committee on national security aimed at assessing the government's measures regarding inter-Korean tensions. The committee, headed by Rep. Park Ji-won, former chief of the National Intelligence Service, includes diplomat-turned-lawmaker Rep. Wi Sung-lak and retired Army Gen. Rep. Kim Byung-joo.

"While it is clear that North Korea is the party that initially triggered unnecessary tensions, our defense ministry must also maintain a thorough readiness and issue a clear statement on North Korea's claims regarding the drone leaflets," party spokesperson Rep. Hwang Jeong-ah said.