SEOUL, South Korea (AP) — North Korea threatened Saturday to shoot down any Japanese planes that enter its airspace, accusing Tokyo of spying near one of its missile launch sites.

The North has designated a no-sail zone off its eastern coast from June 25 to July 10 for military drills, raising concerns that it might test-fire short- or mid-range missiles in the coming days, in violation of a U.N. resolution.

North Korea's air force said Japan's E-767 surveillance aircraft conducted aerial espionage near the Musudan-ri missile site on its northeast coast Wednesday and Thursday.

The military "will not tolerate even a bit the aerial espionage by the warmongers of the Japanese aggression forces but mercilessly shoot down any plane intruding into the territorial air of the (North) even 0.001 mm," the air force said in a statement carried by the country's official Korean Central News Agency.

An official from Japan's Defense Ministry said the country's planes regularly gather information on North Korea but declined to comment on the types of planes used or the locations monitored. He spoke on condition of anonymity, citing government policy.

The threat against alleged Japanese aerial espionage is rare, though the North has regularly complained of U.S. spy missions in its airspace.

Japan is very sensitive to North Korea's missile programs, as its islands lie within easy range. In 1998, a North Korean missile flew over Japan's main island. Tokyo has since spent billions of dollars on developing a missile shield with the United States and has launched a series of spy satellites primarily to watch developments in North Korea.

But in April, another rocket flew over Japan's main island, drawing a strong protest from Tokyo. Pyongyang claims it put a satellite into orbit, while the U.S. and its allies say it was really a test of the country's long-range missile technology.

The launch was one of a series of missile tests in recent months, and the communist regime further raised tensions by conducting a second underground nuclear test in May. Its actions have drawn harsh international condemnation and new U.N. sanctions.

Also Saturday, North Korea accused South Korea of planning to participate in U.S.-led cyber warfare exercises, calling it an "intolerable provocation."

North Korea "is fully ready for any form of high-tech war," said the Committee for the Peaceful Reunification of Korea, which handles relations with South Korea, according to KCNA.

The U.S. leads "Cyber Storm" exercises to test its defenses against computer hackers and invites officials from other countries to participate, but a South Korean Defense Ministry official said he had no information on the exercises. Calls to South Korea's spy agency seeking comment went unanswered on Saturday.