BEIJING -- China on Tuesday denied its fighter jet pilots operated dangerously during an encounter with a U.S. surveillance plane in international airspace in which the American pilot took evasive action to avoid a possible collision.

Spokesman Ren Guoqiang said in a statement on the defense ministry's microblog that the performance of the pilots of the two J-10 fighters was "legal, necessary and professional."

Ren criticized frequent close-in surveillance runs by U.S. planes as raising the chance of accidents, saying such missions "threatened China's national security, harmed China-U.S. sea-air military safety, endangered the safety of pilots from the two sides and were the root cause of China-U.S. sea-air unexpected incidents."

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The U.S. should stop such "unsafe, unprofessional and unfriendly military activities," Ren said, in a repetition of China's standard policy toward U.S. surveillance missions intended at collecting Chinese computer and voice data in hopes of gaining insight into the workings of the People's Liberation Army.

Lt. Cmdr. Matt Knight, a spokesperson for the U.S. Pacific Fleet in Hawaii, told CBS News the incident is still under investigation but, "initial reports from the U.S. aircrew characterized the intercept as unsafe."

Knight said the issue is being addressed with China through "appropriate diplomatic and military channels."

Asked about the incident at a daily briefing, Chinese foreign ministry spokesman Lu Kang said Beijing objected to such missions but remained "committed to building military mutual trust with other countries."

U.S. Navy Capt. Jeff Davis said the Chinese fighters intercepted the U.S. EP-3 surveillance plane Sunday in international airspace between the East China Sea and the Yellow Sea, in an area he described as west of the Korean Peninsula.

Davis said one of the Chinese planes approached at a high rate of speed from beneath the American plane, then slowed and pulled up, prompting the EP-3 pilot to take evasive action. He called the Chinese pilot's move unsafe.

A spokesperson with the U.S. Navy's 7th Fleet told CBS News the incident was "highly unusual," especially since there was no communication between the pilots of the J-10 and EP-3.

"The U.S. and Chinese have good Navy to Navy relationship. Intercepts happen all the time. When something like an unsafe intercept happens it's generally a communication breakdown, but this point they couldn't say what caused this particular incident," the spokesperson said.

China in 2013 declared an air defense identification zone over a partly contested portion of the East China Sea, demanding foreign aircraft declare their presence and follow Chinese orders. The U.S. and others swiftly dismissed the zone as invalid and have largely ignored it. It wasn't clear if Sunday's encounter took place inside the zone.

Such incidents continue to occur despite an agreement between the two sides to prevent them from sparking an international crisis, as happened in April 2001 when a Chinese jet fighter collided with a U.S. EP-3. That led to the death of the Chinese pilot and China's detention of the U.S. air crew for 10 days after their crippled plane landed at a PLA Navy air base on the island province of Hainan.

While China has long chafed at U.S. surveillance operations targeting its military, the PLA itself has been conducting such missions further and further from its home ports.

Earlier this month, China sailed a spy ship through the narrow Tsugaru Strait separating the Japanese islands of Honshu and Hokkaido, while another was spotted last week within Australia's exclusive economic zone where allies Australia and U.S. were conducting major war games.