China scrambled fighter jets on Friday morning after U.S. and Japanese spy and military aircraft had reportedly entered Beijing's newly declared air defense zone over the East China Sea, a Chinese military official said on Friday, as reported by CNN.

Some of the Japanese and U.S. aircraft included F-15 fighter planes, state news agency Xinhua had claimed, 

Chinese air force spokesman Col. Shen Jinke said that they were identifying and monitoring all foreign warplanes in the zone.

"China's air force is on high alert and will take measures to deal with diverse air threats to firmly protect the security of the country's airspace," Shen said.

"It is indeed the right of every country to defend its airspace, and also to make sure that its territorial integrity, its sovereignty, are safeguarded. This is a normal arrangement," added Liu Jieyi, China's ambassador to the United Nations. 

The U.S., South Korea and Japan have ignored such restrictions imposed by China, as a U.S. military official said the flight was part of routine and scheduled operations.

"This is status quo. We are not changing what we are doing. We are not trying to make a point with China. We fly U.S. aircraft daily in international airspace in the region. This is normal," the official said. He added that the aircraft were not B-52s.

"South Korea said its military sent a plane on a routine patrol flight into the zone on Tuesday without alerting China," CNN also reported.

However Caroline Kennedy, the U.S. Ambassador to Japan, told reporters in Tokyo that, "unilateral actions like those taken by China, with their announcement of an East China Sea air defense identification zone, undermine security and constitute an attempt to change the status quo in the East China Sea. It only serves to increase tensions in the region," she said

Japan also rejected China's move.

"Chief Cabinet Secretary Yoshihide Suga [said] his country's Self Defense Force was continuing surveillance patrols of disputed territory in the East China Sea just as it had before China's declaration," CNN reported.