North Korea is developing new missiles capable of carrying tactical nuclear warheads, a Seoul daily reported Tuesday, citing South Korean intelligence authorities.

The JoongAng Ilbo said North Korea has performed a series of test-firings of new short-range missiles since Aug. 14. It was the first time the government had detected Pyongyang developing a tactical nuclear missile, according to the report.

Designated as KN-10, the new ground-to-ground missiles are believed to be designed to carry nuclear payloads, the report said.

“We’ve come to the conclusion that the rockets test-fired three times since last month are new missiles based on their speeds and altitudes,” a senior South Korean government official was quoted as saying.

A South Korean Defense Ministry spokesman denied the report. “Our military authorities don’t have intelligence that missiles North Korea recently test-fired can carry tactical nuclear warheads,” Kim Min-seok said at a press briefing.

While strategic nuclear weapons are designed to be used to destroy large targets such as cities and factories, tactical nuclear weapons are intended to be used on a battlefield. They are developed by placing a relatively smaller nuclear payload on a short-range missile to destroy a military target.