North Korea has increased its stockpile of weapons-grade plutonium from 50kg to 70kg, South Korea’s new defence paper estimates.

The defence paper published on Thursday offered a glimpse into North Korea’s growing number of nuclear weapons and missile stockpiles, as well as its conventional military capabilities, with an estimated North Korean troop strength of 1.28 million active-duty personnel.

North Korea has continued reprocessing spent fuel from its nuclear reactor and possesses about 70kg (154 pounds) of weapons-grade plutonium, up from 50kg (110 pounds) estimated in the previous report, according to the white paper.

According to South Korea’s Yonhap News Agency, approximately 6kg (13 pounds) of plutonium is required to build one nuclear bomb, and the increase in North Korea’s stockpile of the substance is due to operations at the country’s “mainstay nuclear complex” in Yongbyon, north of the capital.

“As North Korea continues to pose military threats without giving up nuclear weapons, its regime and military, which are the main agents of the execution, are our enemies,” the document states, citing Pyongyang’s ongoing weapons development, cyber and military provocations, and its own portrayal of South Korea as an “enemy”.

Previous defence papers have labelled North Korea as the “main enemy”, “present enemy”, or simply “enemy”, particularly during times of tension. Such references have been avoided when relations were improved between Seoul and Pyongyang.

Japan, on the other hand, was described in the paper as Seoul’s “close neighbour” that “shares values” and “common interests”, according to Yonhap.

North Korea has also secured “substantial amounts of highly enriched uranium” and a “significant level of capability” to miniaturise atomic bombs, a description that remains unchanged in the report since the 2018 defence paper.

“Our military is strengthening surveillance as the possibility of an additional nuclear test is rising,” the paper said, citing the restoration last year of previously destroyed tunnels at North Korea’s nuclear test site.

(2nd LD) N. Korea labeled ‘enemy’ again in S. Korea’s defense white paper https://t.co/hX1dJxzxrQ

— Yonhap News Agency (@YonhapNews) February 16, 2023

North Korea’s launches in 2022 of intercontinental ballistic missiles (ICBM), including the new Hwasong-17 ICBM, were noted in the report but further analysis was needed to verify whether Pyongyang had acquired improved missile re-entry technology, the defence paper states.

The paper also outlines South Korea’s deterrence planning, known as the “three-axis”, according to Yonhap.

“The three-pronged system consists of the Korea Massive Punishment and Retaliation (KMPR), an operational plan to incapacitate the North Korean leadership in a major conflict; the Kill Chain preemptive strike platform; and the Korea Air and Missile Defence system,” Yonhap reported.