North Korea’s leap forward in ballistic missile capability may be based on Russian technology and engines illicitly acquired from a factory in Ukraine, experts believe. Military analysts and western intelligence agencies have been trying to explain Pyongyang’s recent string of successful long-range tests. North Korea’s Hwasong-14 missile, tested last month, is unlike other ballistic weapons North Korea has developed, with a purported range capable of striking the continental US. Previous efforts to develop its own Musudan rocket into a viable long-range intercontinental ballistic missile have almost all failed.The “astounding strides” Pyongyang has made can only be explained by assuming it gained access to foreign technology, according to a report published yesterday by the International Institute for Strategic Studies, a defence and security think-tank. “The Hwasong 12 and 14 are powered by a [liquid propellant engine] imported from an established missile power,” said Michael Elleman, senior fellow for missile defence at the IISS. Mr Elleman said North Korea was almost certainly using a modified version of the RD-250 — a Russian-designed missile engine that is only available from two sites, the Energomash plant in Russia and the KB Yuzhnoye design bureau and its closely linked Yuzhmash rocket factory close to Ukraine’s restive east. But it was unclear when they acquired the technology.The engines also appear to have been skilfully modified, said Mr Ellemen, indicating the involvement of foreign engineers. Mr Ellemen’s report points to the Yuzhnoye facility in Ukraine as the likeliest source of the technology. Yuzhmash, the company that produces the rockets designed by Yuzhnoye, denied it could have been the source of the technology. “Missiles and missile components for military use have not been produced since independence,” the company said. A Ukrainian official, meanwhile denied the country was the source of North Korea’s technology, instead blaming Russia. There was no immediate response from Moscow to the claims.