WASHINGTON - Two Chinese SU-30 aircraft carried out what the US military described as an "unprofessional" intercept of a US aircraft designed to detect radiation while it was flying in international air space over the East China Sea."The issue is being addressed with China through appropriate diplomatic and military channels," said US Air Force spokeswoman Lieutenant Colonel Lori Hodge.Hodge said the US characterization of the incident was based on initial reports from the US air crew aboard the WC-135 Constant Phoenix aircraft "due to the maneuvers by the Chinese pilot, as well as the speeds and proximity of both aircraft.""Distances always have a bearing on how we characterize interactions," Hodge said, adding a US military investigation into the intercept was under way.She said the WC-135 was carrying out a routine mission at the time and was operating in accordance with international law.China's Defense Ministry, in a short statement, said the US account "did not accord with the facts."It said that what it described as a US surveillance aircraft was carrying out surveillance activities over the Yellow Sea, and Chinese aircraft went to investigate "in accordance with the law and the rules.""The relevant action was professional and safe," it said.The ministry added that US military ships and aircraft frequently carrying out close-in surveillance is the root cause of safety problems between China and the United States at sea and in the air."We hope that the US side stops relevant surveillance activities, to avoid this kind of incident happening again."Speaking earlier, Chinese foreign ministry spokeswoman Hua Chunying said: "We hope that the US side can respect China's reasonable security concerns."