China maintained a diplomatic calm in the face of US provocation over its newly declared air defence zone above East China Sea islands which it disputes ownership of with Japan.

In open defiance of the declaration the US sent two B52 bombers from a base in Guam to fly through the zone soon after it was announced.

Beijing refused to rise to the bait, however, and merely said that it had monitored the bombers as they flew through the defence zone.

The US has asserted previously that it would not comply with Chinese demands that aircraft flying through the zone identify themselves and accept Chinese instructions.

A brief Chinese Defence Ministry statement yesterday made no mention of a previous warning that it would take "defensive emergency measures" against non-compliant aircraft.

The statement merely warned that "China has the capability to exercise effective control over the relevant airspace."

The US claimed that the flights had been a training mission and insisted that they had not been flown as a provocation.

But Chinese public reaction to the bomber flights was predictably angry, with some recalling the 2001 collision between a Chinese fighter and a US surveillance plane in international airspace off China's south-eastern coast.

Other commentators pointed out that Beijing had merely been responding in kind to Japan's recent extension of its own air defence zone in the East China Sea.

The Japanese zone overlaps extensively with the new Chinese zone, especially since Japan extended it westwards by 14 miles in May.