Several Japanese aircraft entered China's Air Defense Identification Zone (ADIZ) over the East China Sea on Wednesday and carried out extensive reconnaissance, according to the Chinese Air Force.

Chinese planes conducted necessary tracking and monitoring of the foreign military planes, said Chinese Air Force spokesman Shen Jinke on Thursday.

The Japanese F-15 aircraft twice attempted to approach Chinese planes that were conducting a routine patrol in the ADIZ, and the Chinese planes took "reasonable, proper and restrained" measures to cope with the threat in the airspace, Shen said.

The spokesman reaffirmed that the establishment of the ADIZ is a purely defensive move to safeguard national security, normal order and the safety of flights over the East China Sea.

Chinese air force planes have been regularly patrolling the ADIZ since it was established in November last year and have exercised effective control over all objects flying over the zone.

"The air force has carried out monitoring and identification of foreign military aircraft entering the zone and has taken corresponding measures to different threats, effectively safeguarding national air defense security," Shen said.