The self-proclaimed nuclear power North Korea has reported that it has made further progress in the development of long-range missiles with hypersonic warheads. The missile authority successfully tested a medium-range missile with a new solid-fuel drive on Sunday, state media reported on Monday. The missile was loaded with a manoeuvrable hypersonic warhead. No details of the flight distance were given. Both South Korea and Japan registered the test. South Korea’s military spoke of a suspected medium-range missile. It had flown around 1,000 kilometres before falling into the water in the Sea of…