NEW YORK - Two long-range US B-52 bombers flew over a disputed island chain in the East China Sea without informing Beijing, a major American newspaper reported Tuesday, citing US officials. The US move is seen as a direct challenge to China and its establishment of an “air defence identification zone” on Saturday when Beijing said aircraft obey its rules or face “emergency defensive measures”.

The planes flew out of Guam and entered the new Chinese Air Defence Identification Zone at about 7pm Washington time Monday, according to The Wall Street Journal.

Over the weekend, China said it was expanding its air-defense zone to include the island chain, which is claimed by both Beijing and Tokyo but administered by Japan. The islands, the source of growing friction in the region, are known as the Diaoyu in China and Senkaku in Japan. U.S. has more than 70,000 troops stationed in Japan and South Korea. US defence officials earlier had promised that the US would challenge the zone and wouldn’t comply with Chinese requirements to file a flight plan, radio frequency or transponder information.

The flight of the B-52s, based at Anderson Air Force Base in Guam, were part of a long-planned exercise called Coral Lightning, the report said. The bombers weren’t armed and weren’t accompanied by escort planes. But the routine flight took on new significance with China’s weekend announcement, and it counters Beijing’s attempts to strengthen its influence over the region, it was pointed out. China had warned that aircraft that don’t comply could be subject to a military response. The US official said that China didn’t make contact with the B-52s as they flew over the islands. The planes returned to Guam after the exercise.

“The planes flew a pattern that included passing through the ADIZ,” the official said. “The flight was without incident.” US officials said they believe they had to challenge the ADIZ to make clear they don’t consider the Chinese move to be appropriate. But they said they don’t believe U.S. flights over the island will create a military conflict. China is now requiring aircraft flying in the region to register their flight path with the Foreign Ministry, identify their transponder and their radio  frequency. Colonel Steve Warren, the Pentagon spokesman, said the US wouldn’t comply with those requirements.