SEOUL, South Korea (AP) — North Korea fired a ballistic missile toward its eastern waters on Friday, South Korea’s military said, its latest weapons demonstration that came days after U.S. and South Korean warplanes conducted joint drills that North Korea viewed as an invasion rehearsal.

South Korea’s Joint Chiefs of Staff said the launch occurred Friday but gave no further details, such as what type of weapon was fired and how far it flew.

The U.S. flew nuclear-capable bombers and advanced stealth jets near the Korean Peninsula for joint training with South Korean warplanes on Tuesday. North Korea typically calls such military exercises by the U.S. and South Korea an invasion rehearsal.

South Korea’s Defense Ministry earlier said the drills were part of a bilateral agreement on a U.S. resolve to defend its Asian ally with all available military capabilities, including nuclear.

The training came after North Korea recently claimed to have conducted key tests needed to develop its first military spy satellite and a new strategic weapon, a likely reference to a more mobile intercontinental ballistic missile.

North Korea said it launched a pair of rockets Sunday to test cameras and other systems for the development of its first military reconnaissance satellite. Its state media published low-resolution photos of South Korean cities as viewed from space.

Some civilian experts in South Korea and elsewhere said the photos were too crude for surveillance purposes and that the launches were likely a cover for tests of North Korea’s missile technology. South Korea’s military said North Korea fired two medium-range ballistic missiles.

Such assessments have infuriated North Korea, with the powerful sister of North Korean leader Kim Jong Un issuing crude insults of unidentified South Korean experts. Kim Yo Jong said there was no reason to use an expensive, high-resolution camera for a single-shot test and that North Korea’s space agency used two old missiles as space launch vehicles.

North Korea has test-launched a barrage of missiles this year, including nuclear-capable ballistic weapons designed to strike the U.S. mainland and its allies South Korea and Japan. North Korea said it was compelled to carry out such tests to respond to previous military drills between the United States and South Korea.