North Korea’s newly unveiled nuclear-powered submarine, reportedly made with Russian technology, could pose a major security challenge to neighbour South Korea and its ally the US, experts said.The Korean Central News Agency on Saturday released photos of what it called an under-construction “nuclear-powered strategic guided missile submarine",

North Korea has long vied for nuclear-powered submarines, which would allow it to fire missiles from underwater. Advanced detection of the weapons is difficult, making the country’s construction of the warships worrisome.

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.