SEOUL, South Korea — North Korea said Monday it fired a test satellite in an important final-stage test for the development of its first spy satellite, a key military capability coveted by its leader Kim Jong Un along with other high-tech weapons systems. The rocket carrying the test satellite was launched Sunday to assess the satellite’s photography and data transmission systems, KCNA said. South Korea, Japan and U.S. authorities said Sunday they had detected a pair of ballistic missile launches by North Korea from its northwestern Tongchang-ri area, where the North’s satellite launch pad is located.