China has denied accusations by the United States that its fighter jets conducted an "unprofessional" intercept of an American aircraft flying in international airspace.

The U.S. Air Force said Friday that two Chinese fighter Su-30 fighter jets had intercepted a U.S. radiation-detecting plane in international airspace over the Yellow Sea off the Korean Peninsula.

The U.S. aircraft, a U.S. WC-135 Constant Phoenix, known colloquially as a "nuke sniffer," was intercepted Wednesday during what the air force termed "a routine mission."