The submarine could significantly escalate security concerns on the Korean peninsula and in the Taiwan Strait, experts say North Korea's construction of a nuclear-powered submarine could significantly escalate security concerns on the peninsula and in the Taiwan Strait,

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.

Last week's accidental shelling of a South Korean village occurred less than 20 miles from the border of the nuclear-armed North.