CHINA has sent fighter jets and an early warning aircraft into its newly declared maritime air defence zone.

The move came days after the US, South Korea and Japan all sent flights through the airspace in ­defiance of rules Beijing says it has imposed in the East China Sea.

China's air force sent the warplanes on normal air patrols in the zone but it is not known whether they encountered any foreign aircraft.

The US, Japan and South Korea have said they have sent flights through the zone without encountering any Chinese response since Beijing announced the creation of the zone last week.

Without prior notice, Beijing began demanding on Saturday that passing aircraft identify themselves and accept Chinese instructions or face consequences.

But when tested days later by US B-52 flights - with Washington saying it made no effort to comply with China's rules, and would not do so in the future - Beijing merely noted, belatedly, that it had seen the flights and taken no further action.

The zone is seen primarily as China's latest bid to bolster its claim over a string of uninhabited Japanese-controlled islands in the East China Sea - known as Senkaku in Japan and Diaoyu in China.