North Korea fires missile as 'countermeasure' to U.S.-South Korea military exercises

North Korea fired a short-range missile into the sea and tried to jam GPS navigation signals in South Korea, Seoul officials said, hours after U.S., South Korean and Japanese leaders pledged to work closer together to prevent North Korea from advancing its nuclear and missile programs.

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North Korea's official Korean Central News Agency said Saturday that authoritarian leader Kim Jong Un expressed "great satisfaction" after observing a successful live-fire test of a new anti-air weapons system, but didn't say when and where the test took place. South Korean military officials on Friday said they detected the North firing a surface-to-air missile off its east coast, and it wasn't immediately clear if the two were linked.

South Korean officials said the attempt to jam GPS signals, which began Thursday, did not cause any major disruptions of South Korean military, aviation and sea transport and telecommunication systems. However, more than 130 fishing boats reported problems with their navigation systems and some were forced to return to their ports, the Ministry of Oceans and Fisheries said.

South Korea's defence ministry called the jamming attempt a provocation that threatened public safety and military operations in the South. A ministry statement warned North Korea to immediately stop the jamming efforts or face unspecified consequences.

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South Korea has blamed North Korea for several previous jamming attempts. This week's jamming signals are the first since 2012, according to South Korea's Science Ministry. North Korean state media had no immediate comment.

The North's launch of a surface-to-air missile on Friday came three days after it launched a projectile that hit land in its northeast. South Korea's Defence Ministry and Joint Chiefs of Staff offered no immediate comment on whether KCNA's report on Saturday was related to Friday's launch.

North Korea has launched a number of short-range missiles and other projectiles since the start last month of annual South Korea-U.S. military drills it views as a rehearsal for an invasion. It also has repeated threats of nuclear strikes on Seoul and Washington and warned it will test a nuclear warhead and ballistic missiles capable of carrying it.

"If the United States continues [with military exercises with the South], then we have to make the countermeasures also, as I told you. So, we have to develop and we have to make more deterrence, nuclear deterrence," the North's ambassador to the United Nations, So Se Pyong, told Reuters in Geneva.

This year's drills, set to run until late this month, are the biggest ever and come after North Korea conducted a nuclear test and long-range rocket launch earlier this year.

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In Washington, U.S. President Barack Obama met Thursday with the leaders of South Korea and Japan to discuss ways of countering North Korea's nuclear threat. Obama also met Chinese President Xi Jinping and both called for North Korea to give up its nuclear weapons. China also agreed to fully implement recent economic restrictions imposed by the U.N. Security Council against North Korea. The Asian leaders are in Washington for a two-day nuclear summit that opens Friday.