TOKYO/SEOUL (Reuters) - North Korea fired a missile that flew over Japan and landed in waters off the northern region of Hokkaido early on Tuesday, South Korean and Japanese officials said, marking a sharp escalation of tensions on the Korean peninsula. The test, which experts said appeared to have been a recently developed intermediate-range Hwasong-12 missile, came as U.S. and South Korean forces conduct annual military drills on the peninsula, against which North Korea strenuously objects. Earlier this month, North Korea threatened to fire four Hwasong-12 missiles into the sea near the U.S. Pacific territory of Guam after U.S. President...