BEIJING -- China on Thursday rejected U.S. claims that its fighter jets maneuvered unsafely when they intercepted an American Navy reconnaissance plane over the South China Sea, and demanded that the U.S. end such missions close to Chinese territory.

The Chinese jets monitored the U.S. plane from an acceptable distance and operated in a safe and professional manner, Foreign Ministry spokesman Hong Lei told journalists at a regularly scheduled news briefing.

"According to the related Chinese authorities, the U.S. allegation is not true," Hong said.

Frequent reconnaissance missions by U.S. Navy vessels' aircraft off the Chinese coast "jeopardizes China's sea and air safety," Hong said. "We urge the U.S. to immediately stop spying activities and prevent such events from happening again," he said.

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The Pentagon said two Chinese J-11 fighters flew within about 50 feet of the U.S. EP-3 Aries aircraft on Tuesday, forcing the U.S. pilot to descend sharply to avoid a collision. It said the U.S. plane was conducting routine operations in international airspace.

It characterized the incident as an unsafe intercept and said it is being reviewed.

The U.S. has sought to prevent such confrontations through frequent communication and the signing of an agreement on handling unexpected encounters at sea and in the air.

However, such incidents may now be on the increase as the U.S. challenges China's claims that its newly created artificial islands in the South China Sea enjoy legal rights to territorial seas and airspace. China says it is entitled to keep watch over such airspace and seas.

China has long been irked by U.S. reconnaissance missions off the Chinese island province of Hainan, which sits at the northern end of the South China Sea and is home to a number of highly sensitive naval and air installations.

In 2001, a collision between a Chinese fighter jet and a U.S. surveillance plane in which the Chinese pilot was killed and the American crew detained on Hainan led to a crisis in U.S.-China relations.