New photos show North Korea's apparent progress in the development of a nuclear-powered submarine as Kim Jong Un condemns South Korea's efforts.

North Korea's state media released photos Thursday of what it said was the hull of a nuclear submarine. Its leader denounced South Korea's plans to build its own subs as "an offensive act."

The debut followed the North’s first test of a new surface-to-air missile and the arrival of a U.S. nuclear-powered attack sub for a port call in South Korea.

North Korea displayed apparent progress in the construction of a nuclear-powered submarine, with state media photos showing a largely completed hull as leader Kim Jong Un condemned rival South Korea’s push to acquire the technology.