North Korea mentioned for the primary time on Thursday that it had examined know-how for launching a number of nuclear warheads with a single missile, days after President Vladimir V. Putin of Russia visited the North and raised the prospect of expanded navy and technical cooperation.

The check on Wednesday was “aimed toward securing the MIRV functionality,” the North’s state-run Korean Central Information Company reported. MIRV stands for “a number of independently targetable re-entry automobile,” a missile payload containing a number of warheads, every of which will be despatched to a distinct goal. The report mentioned the check had concerned a part of a MIRV system, not a full-fledged multiple-warhead missile.

Since North Korea’s chief, Kim Jong-un, hosted Mr. Putin for talks final week, officers and analysts have expressed concern that their deepening ties would encourage Mr. Kim to embark on an formidable improve to his nuclear arsenal.

MIRV functionality would mark a drastic enhance in the threat the North poses to the USA and its allies, as a result of a high-speed ballistic missile splitting into a number of nuclear warheads, in addition to decoys, is tougher for missile protection techniques to intercept.

South Korean officers known as the North’s Wednesday check a failure quickly after it occurred, saying {that a} missile had exploded over waters east of the nation after flying 150 miles.

It is a growing story.