Foreign Ministry spokesman says China will keep close watch and take action if necessary

Beijing released further details on Friday and voiced "strong dissatisfaction" about a close encounter on Wednesday involving a US spy plane above the South China Sea.

The incident involved a US navy P-8A surveillance plane that flew near islands and reefs, including the Yongshu Reef of China's Nansha Islands, on a reconnaissance mission, Foreign Ministry spokesman Hong Lei said at a daily news conference.