Underwater test-fire of a strategic submarine ballistic missile at an undisclosed location in North Korea on April 23, 2016. Photo: AFP via KCNA

The US Navy flew a spy plane near the coast of North Korea to track for signs of a submarine-based missile launch, a South Korean news network said Tuesday.

Cable network Channel A said that a US EP-3 reconnaissance aircraft stationed in Japan recently flew near the eastern coast of North Korea checking for signs of an impending missile launch from a North Korean sub.

The reported mission follows word that North Korea is escalating efforts to develop a submarine-launched ballistic missile (SLBM) fleet. South Korea is also in serious discussions to build nuke-powered hunter-killer submarines with US help to counter the threat from Pyongyang.

Yonhap, in a separate story, quoted a Pentagon spokesman as saying the US is “well postured” to deal with a possible submarine-launched ballistic missile from North Korea. “I can’t comment on any matters of specific intelligence regarding North Korea,” Pentagon spokesman Army Col. Robert Manning said, “but I will tell you that within the deep arsenal that we have of capabilities, we’re well postured to deal with that.”

Anti-sub warfare drills slated

The New York Times reported on Monday that the US, Japan and South Korea will be conducting a joint exercise to track such hard-to-detect SLBMs by North Korea.

“The drill is taking place over two days in waters between Japan and the Korean Peninsula, said South Korea’s Joint Chiefs of Staff, and will involve destroyers from the three nations doing computer-simulated training to track submarine missile launchings by North Korea,” the Times said.

NK has 5 sub-missile prototypes

A Japanese newspaper also said last week that North Korea has finished developing five prototypes for an upgraded SLBM. A test of a new missile is expected soon.

38 North, a respected Johns Hopkins University website that analyzes North Korean affairs, recently reported that North Korea’s SLBM program is making progress.

Commercial satellite imagery from the second half of November shows that a second submersible ballistic missile test stand barge (a platform that allows for underwater missile launches outside submarines) at the North’s Nampo Navy Shipyard is being readied for service.

38 North analyst Joseph S. Bermudez said in a December 1 assessment  that this is “a strong indicator that Pyongyang is advancing its SLBM program.”