North Korea is believed to have extracted up to 50 kilograms (110 pounds) of plutonium that can build as many as seven nuclear weapons, according to a South Korean Defence Ministry report released by a lawmaker on Thursday.
The communist nation is also working to make a small and lightweight nuclear warhead that can be mounted atop a ballistic missile, said the ministry, according to an internal assessment released by Song Young-sun, a lawmaker from the main opposition Grand National Party.
The assessment was made in a top military officials' meeting a day after the North's October 9 nuclear test.
Currently, the North is believed to have built a nuclear warhead weighing some two to three tons, said the ministry. To be mounted on a missile, the warhead would need to be less than one ton, the ministry said.
The North can also drop nuclear bombs with its Russian-made bombers, said the ministry, adding that the North has 82 Il-28 bombers at bases in Uiju and Jangjin.
The North stunned the world in 1998 by firing a long-range ballistic missile over Japan into the Pacific Ocean and it also test-fired seven missiles in July, including a long-range missile believed capable of reaching the United States that crashed shortly after launch.