North Korea on Monday claimed it had successfully launched a new kind of medium long-range rocket that can carry a large, heavy nuclear warhead. Outside observers saw an important technological jump in Sunday’s test. They said the rocket flew higher and longer than any other missile tested by North Korea. The missile flew for half an hour on Sunday. It reached a very high altitude before landing in the Sea of Japan, close to Russia, according to Japanese and Russian officials. The governments of South Korea, Japan, the U.S. and Russia condemned the missile test.