North Korea fired what appeared to be a submarine-launched ballistic missile, Seoul said yesterday, just days before Washington and Pyongyang were set to resume long-stalled nuclear talks.

Pyongyang frequently couples diplomatic overtures with military moves, as a way of maintaining pressure on negotiating partners, analysts say, and may believe this weapons system gives it added leverage.

A proven submarine-based missile capability would take the North’s arsenal to a new level, allowing deployment far beyond the Korean peninsula and a second-strike capability in the event of an attack on its military bases.

The South’s Joint Chiefs of Staff said it detected a ballistic missile early Wednesday fired in an easterly direction from the sea, northeast of the North Korean port of Wonsan.

The missile was “believed to be one of the Pukkuksong models”, the JCS said in a statement, referring to a line of submarine-launched ballistic missiles (SLBM) under development by the North.

Launches like this “are not helpful to efforts to ease tensions on the Korean peninsula and we urge North Korea again to stop immediately,” it added. The North carried out a successful test of the solid-fuel Pukkuksong-1, also known as KN-11, in August 2016 which flew around 500 kilometres.

In July, North Korean state media had published pictures of Kim Jong Un inspecting a new type of submarine, fuelling concerns that Pyongyang was pushing ahead with an SLBM programme.

Analysts say the missile is believed to have been fired at a lofted angle, adding it is likely an intermediate-range ballistic missile with an actual flight range of around 2,000 kilometres.

Vipin Narang, an associate professor at Massachusetts Institute of Technology, drew a line between a recent series of launches by Pyongyang and Wednesday’s test, calling it “an explicitly nuclear weapons system”.

The United States said it was monitoring the situation on the Korean peninsula.

A part of the missile landed in waters within Japan’s exclusive economic zone—a 200-kilometre band around Japanese territory—Tokyo said. “The launching of ballistic missiles violates UN Security Council resolutions and we strongly protest and strongly condemn it,” Prime Minister Shinzo Abe told reporters.

The North is banned from ballistic missile launches under UN Security Council resolutions.

The launch came a day after the North’s Vice Foreign Minister Choe Son Hui said Pyongyang had agreed to hold working-level talks with Washington later this week.

The two sides will have “preliminary contact” on Friday and hold negotiations the following day, Choe said in a statement carried by the official Korean Central News Agency.