North Korea has expanded ballistic missile units and strengthened its special forces with modernized equipment, along with exercises to attack strategic targets, such as South Korea's presidential office.

According to the Defense Ministry's white paper on Tuesday, North Korea has increased missile brigades under its strategic force command from nine units in 2018 to 13.

The units are believed to operate short-range ballistic Scud missiles, Rodong missiles with a range of around one-thousand-300 kilometers and Musudan missiles with ranges of over three-thousand kilometers.

Pyongyang is assessed to have 50 kilograms of weapons-grade plutonium and a considerable amount of highly-enriched uranium(HEU) in its possession. In addition, its technology to miniaturize a nuclear warhead has reached a "considerable" level.

The paper also said the North is constructing a new three-thousand-ton submarine that can carry a submarine-launched ballistic missile(SLBM).