North Korea has tested a nuclear-capable underwater attack drone in response to joint naval exercises involving South Korea, the United States and Japan, state media say. The allies announced the drills after Pyongyang said on Sunday that it had tested a new solid-fuel missile fitted with a hypersonic warhead. Tensions on the Korean Peninsula have been elevated in recent months amid Pyongyang’s repeated weapons tests and moves by its leader Kim Jong Un to roll back efforts towards reconciliation with South Korea.