An undated photo released on 10 October 2022 by the official North Korean Central News Agency (KCNA) shows a military striking drill of long-range artillery sub-units on the front and flying corps of the Korean People's Army (KPA), carried out to check and assess the war deterrent and nuclear counterattack capability of the country, amid ongoing joint military exersizes involving US and South Korean forces in the waters near the Korean Penninsula. EPA-Yonhap

The office of President Yoon Suk-yeol said Monday the Korean Peninsula and Northeast Asia are facing a "grave" security situation, hours after North Korea said it practiced transporting nuclear warheads and firing a nuclear-capable ballistic missile from under a reservoir.

"It is important to accurately recognize the grave security reality on the Korean Peninsula and in Northeast Asia and prepare appropriately for it," a presidential official said in a notice to reporters.

"Protecting the lives and safety of people is not about words, but it is a real-life problem."

The remark came hours after the North said via its official Korean Central News Agency that military units handling "tactical nukes" staged an exercise of launching a ballistic missile "under the simulation of loading tactical nuclear warheads at a silo under a reservoir."

"The drill was aimed at confirming the order of taking tactical nuclear warheads out and transporting them and of managing them in a rapid and safe way at the time of operation, checking the reliability of the overall management system, making the units acquire launching capabilities of the ballistic missile at the underwater silos and inspecting their rapid response posture," the KCNA said.