North Korea said on Tuesday that it had tested a new ballistic missile with a “super-large warhead,” the most recent development in an arms race with South Korea as the countries vie to introduce weapons of increasingly destructive power.

Two of the new missiles, known as the Hwasong-11Da-4.5, were launched on Monday, each with a dummy warhead that weighed 4.5 tons, the North’s official Korean Central News Agency said. ​Ballistic missiles often carry warheads that weigh less than a ton.

South Korea already has similar missiles that can deliver large warheads. Col. Lee Sung-jun, a spokesman for the South’s military, said the North’s Hwasong-11 series missiles were believed to be capable of carrying payloads of half a ton to 2.5 tons, but that it was “theoretically possible” to modify them to deliver a 4.5-ton payload.

But Colonel Lee accused North Korea of deceptively exaggerating its capabilities in the Tuesday report. One of the two missiles the North launched on Monday crashed in an empty field after an “abnormal” flight, he said.

The United States has accused North Korea of supplying Hwasong-11 missiles to Russia for use against Ukraine. ​Both Pyongyang and Moscow have denied trading in arms, which would violate United Nations Security Council resolutions imposed on the North because of its nuclear weapons program.

The launch Monday was the second major weapons test reported by the North since its leader, Kim Jong-un, hosted President Vladimir V. Putin of Russia for talks in Pyongyang on June 19. Last week, North Korea claimed for the first time that it had tested technology for launching several nuclear warheads with a single missile; the South cast doubt on that report, too.