The USS Nautilus was the world's first nuclear-powered submarine. It participated in scientific and military operations around the world.

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.

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,