North Korean leader Kim Jong-un supervised a successful test of a new engine for an intercontinental ballistic missile (ICBM), its state media has claimed.

Tension has been high in the region after a nuclear test and a long-range rocket launch by North Korea earlier in the year. Last month, the UN security council unanimously approved the toughest sanctions against the regime in two decades over its arms programmes. There have also been large-scale drills by South Korean and US troops.

For the test, the engine was ignited at Kim’s command “and released a fiery blast, and the rocket fulfilled all required conditions”, the North’s KCNA news agency said.

According to KCNA, Kim said: “Dear comrades, now we can mount an ever more powerful nuclear warhead on a new intercontinental ballistic rocket and put the den of evil in the United States and all over the world within our strike range.”

The test was conducted at the country’s missile station near its west coast where in February it launched a long-range rocket that put an object into space orbit, it said.

North Korea said in March that it had miniaturised a nuclear warhead to be mounted on ballistic missiles and conducted a simulated re-entry test of a ballistic missile, which could indicate advances in its ICBM programme if true.

But South Korean officials questioned those assertions and said the North was several years away from developing an ICBM. The US said there was no proof of the North’s claims and called on Pyongyang to halt actions that fuelled tension.

The North conducted its fourth nuclear test in January and the rocket launch in February in defiance of international warnings and past UN sanctions, triggering the new security council resolution that imposed more punishment.

Despite the claims, the North has yet to conduct a flight-test of a long-range missile or an ICBM that would demonstrate successful mastery of the technology needed to bring a missile back into the atmosphere and hit a target with precision.

The North claimed its January nuclear test was a successful hydrogen bomb test, but many experts and officials in the South and the US said the blast was too small to have been from a successful such test.