kim jong un
kim jong unReuters

North Korea said Saturday it had successfully tested a new engine for an intercontinental ballistic missile (ICBM) that would "guarantee" a nuclear attack on the United States, as the isolated country continues to oppose the international community's calls to reign in its nuclear programme. The test was conducted under the personal guidance of North Korean leader Kim Jong Un, who threatened to reduce the U.S. to "ashes" with new ICBM rockets, the state media reported. 

Pyongyang claimed success in the "jet test of a new type high-power engine of intercontinental ballistic rocket" that was carried out at the Sohae Space Center, according to the Korean Central News Agency. 

"The great success made in the test provided a firm guarantee for mounting another form of nuclear attack upon the U.S. imperialists and other hostile forces, and made it possible to have access to more powerful means capable of reacting to nukes in kind," Kim Jong Un said, according to Yonhap news agency that cited KCNA. 

North Korea had claimed earlier it had miniaturised nuclear warheads to fit on ICBMs. In February, it had conducted a rocket launch ostensibly to launch a satellite in space, but this was seen by the United States and other nations as a test to launch ballistic missiles. 

"Now the DPRK can tip new type intercontinental ballistic rockets with more powerful nuclear warheads and keep any cesspool of evils in the earth, including the U.S. mainland, within our striking range and reduce them to ashes so that they may not survive in our planet," Kim reportedly said, using the official abbreviation for the country. 

North Korea has amped up its aggression against the U.S. and South Korea in recent months following heavy UN sanctions for its nuclear test in January as well as the joint military exercise between the two allies.