BEIJING (Reuters) - Japanese fighter jets shadowed Chinese aircraft patrolling over disputed waters, China's Ministry of Defense said on Thursday, in the latest flare-up of a spat over air space that has deepened a rift between the two countries.

Tension has been high between Asia's two largest economies in recent months, with each accusing the other of flying military aircraft too close to its own jets in a long-running territorial dispute.

Both sides claim a string of Japanese-administered islets in the East China Sea, known as Senkaku in Japan and Diaoyu in China. Beijing declared an air defense zone covering most of the East China Sea last year, sparking protests from Japan and the United States.

China took "necessary measures" when numerous Japanese planes entered its East China Sea Air Defense Identification Zone during China's routine air patrols on Wednesday to safeguard "order and security", the Ministry said on its website.

"Japanese F-15 fighter jets twice attempted to shadow Chinese patrol planes. China's air force took reasonable, fair and restrained measures to respond to the threat," the Ministry said, citing air force spokesman Colonel Shen Jinke.

Japan's Ministry of Defense told Reuters it had no information on the incident.

In June, China summoned Japan's defense attache to lodge a protest after the two countries traded accusations over the conduct of military jets.

Japan warned in a report this week that China's defense budget soared fourfold over the past decade to 808 billion yuan (£77.8 billion), while Japan's defense spending dipped by 1.9 percent over the same period to 4.78 trillion yen (£27.7 billion).

China said Japan was exaggerating the threat posed by its military spending to justify its own build-up.

(Reporting by Michael Martina, Additional reporting by Elaine Lies in Tokyo; Editing by Clarence Fernandez)