Chinese troops asked a U.S. military jet approaching the Nansha Islands to change course by radio, a foreign ministry spokesperson confirmed on Friday.
"Chinese troops acted upon the rules and asked the U.S. aircraft to leave," spokesperson Hong Lei told a daily press briefing.
Hong's comments came after a US P-8A anti-submarine and maritime surveillance aircraft flew over waters off China's Nansha Islands on Wednesday.
"It must be pointed out that the reconnaissance conducted by the U.S. military aircraft poses a potential threat to the security of China's maritime features," Hong said.
"The move is very likely to cause miscalculation, or even untoward maritime and aerial incidents," he said, calling the occurrence irresponsible, dangerous and detrimental to regional peace and stability.
Hong said China expresses strong dissatisfaction.
"We call on the United States to act in strict accordance with international law, and refrain from taking any risky or provocative action," Hong said.
China will keep a close watch on the situation and take proper measures to protect the security of its territory, Hong said.