Chinese military officials have accused US bombers of flying too close to the country and operating in its airspace during a mission off South Korea.

Pilots of the US Air Force B-1B Lancer bomber were forced to respond to Chinese air traffic controllers during a flight about 70 nautical miles southwest of South Korea's Jeju Island.

American officials told CNN the pilots told the Chinese controllers they were conducting 'routine operations in international airspace and did not deviate from their flight path'.

Chinese military officials have accused a US B-1B Lancer bomber of flying too close to the country and operating in its airspace during a mission off South Korea

This map shows where the bomber was flying when Chinese officials contacted the American pilots during the stand off

The network revealed the tense moment was the result of the bombers had actually entered the Chinese Air Defense Identification Zone - a controversial area of sky over the East China Sea.

The airspace also covers islands claimed by Japan, and it is not officially recognized by the US.

'Pacific Air Forces ... did not recognize the Chinese Air Defense Identification Zone when it was announced in November of 2013, and does not recognize it today,' US Pacific Air Forces spokesman Major Phil Ventura told CNN.

This map shows how the different airspaces in the area in question are divided up by the different countries in the region

The US B-1B Lancer bomber was seen flying in formation with Japan Air Self Defense Force F-15s on March 21

'The ADIZ has not changed our operations.'

Chinese authorities demand airplanes flying over or through the airspace must first notify officials.

US Air Force sources said B-1 bomber was carrying out training operations with Japanese and South Korean jets in recent days.

On March 21, the American bomber was seen flying in formation with Japan Air Self Defense Force F-15s.