Image copyright AP Image caption US aircraft may follow several regional carriers complying with China's new rules

The US says it expects its civilian aircraft to observe China's rules in an air defence zone in the East China Sea.

A US statement said this did not mean the US accepted China's requirements in the zone covering territory claimed by China, Japan, Taiwan and South Korea.

China wants all aircraft there to file flight plans and identify themselves.

The US, Japan and South Korea say they have flown military aircraft in the area unannounced. But China said it scrambled fighter jets on Friday.

The move was to monitor US and Japanese aircraft in the zone.

'Firm but calm'

The air defence identification zone (ADIZ) covers a vast area of the East China Sea, including a group of islands claimed by Japan, China and Taiwan.

South Korea claims a submerged rock, known as Ieodo, also within the zone.

The establishment of the ADIZ has caused widespread anger, with the US state department calling it "an attempt to unilaterally change the status quo in the East China Sea" which will "raise regional tensions and increase the risk of miscalculation, confrontation and accidents".

But on Friday, the state department said the US government "generally expects that US carriers operating internationally will operate consistent with Notams [Notices to Airmen] issued by foreign countries".

Air defence identification zones Zones do not necessarily overlap with airspace, sovereign territory or territorial claims

States define zones, and stipulate rules that aircraft must obey; legal basis is unclear

During WW2, US established an air perimeter and now maintains four separate zones - Guam, Hawaii, Alaska, and a contiguous mainland zone

UK, Norway, Japan and Canada also maintain zones Source: aviationdevelopment.org Q&A: China-Japan islands row Viewpoints: China air zone tensions

It added: "Our expectation of operations by US carriers consistent with NOTAMs does not indicate U.S. government acceptance of China's requirements for operating in the newly declared ADIZ."

Japan has instructed its aircraft not to observe China's rules. But a number of regional commercial airlines - including Singapore Airlines, Qantas and Korean Air - have said they will comply.

China announced on Thursday it was deploying warplanes in the area for surveillance and defence.

Then on Friday, Air Force spokesman Col Shen Jinke said warplanes had been scrambled that morning to monitor two US surveillance aircraft and 10 Japanese planes - including early warning aircraft, surveillance aircraft and fighter jets - crossing through the ADIZ.

Col Shen said the jets had tracked the flights and identified the planes, state media reports.

Japanese officials gave no details of the flights, but said they were continuing to conduct routine operations in the region and had encountered no "abnormal instances so far".

Earlier, China's foreign ministry spokesman Qin Gang said China had a right to patrol the region and that the ADIZ was not aimed at any specific country.

"If some worry has emerged about the situation, it's agitated by some individual countries," he told a regular briefing.

If disputes existed, China wanted to solve them through "peaceful means via friendly negotiation," he said.

Image copyright AP Image caption China, Japan and Taiwan all claim islands lying within the air defence zone

Japanese Prime Minister Shinzo Abe said on Friday that Japan would respond "firmly but in a calm manner" to China's move, the Kyodo news agency reports.

Foreign Minister Fumio Kushida said the issue would be discussed with US Vice-President Joe Biden, who is due to begin a three-day visit to Japan on Monday.

The disputed group of uninhabited islands in the zone are known as Senkaku in Japan and Diaoyu in Chinese.

They are controlled by Japan, but have been the subject of rising tensions in recent years because of their proximity to important shipping lanes, fishing grounds and potential fossil fuel reserves.

South Korea has complained to China that the ADIZ also overlaps its own similar defence zone, and encompasses the Ieodo rock.