Did Russia help build North Korea’s latest nuclear submarine?

North Korea’s construction of a nuclear-powered submarine could significantly escalate security concerns on the peninsula and in the Taiwan Strait, experts have warned, as speculation mounts over Russian involvement in the project.

Images released by North Korea’s state media on Saturday showed leader Kim Jong-un inspecting what it described as a “nuclear-powered strategic guided missile submarine” at an undisclosed shipyard. The location, timing of the visit and details about the vessel’s size were not revealed.

If confirmed, it would be the first time North Korea had revealed a look at its nuclear-powered submarine, experts said.

While receiving a briefing from officials, Kim was pictured next to the submarine shown only partially in the pictures, making it difficult to discern its tonnage and shape.

But Moon Keun-sik, a professor at Hanyang University and a former South Korean navy submarine captain, said the images suggested the visit took place at the Sinpo Shipyard in South Hamgyong province.

The naval vessel appeared to be a 6,000-ton-class or 7,000-ton-class one which could carry about 10 missiles, Moon noted, adding that the use of the term “strategic guided missile” meant it would carry nuclear-capable weapons.