North Korea has unveiled for the first time what it says is a nuclear-powered submarine under construction, a weapons system that can pose a major security threat to South Korea and the US.

North Korea has publicly unveiled the construction of a nuclear-powered submarine, a weapons system that could pose a serious security threat to South Korea and allies if successfully developed, due to its ability to operate submerged for months.

North Korea could be building a nuclear-powered submarine, possibly with Russian help, raising security concerns for the US and South Korea over its stealth attack capabilities