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 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.

SEOUL, South Korea — North Korea unveiled for the first time a nuclear-powered submarine under construction, a weapons system that can pose a major security threat to South Korea and the U.S.