China's activity in the contested South China Sea is "hindering" Filipino companies from exploring natural resources in the region, Philippines Foreign Secretary Enrique Manalo said during a talk at Chatham House in London on Tuesday.

"The Philippines has no major external security threats, but has turned itself into a country that undermines regional peace and stability through a militarization carnival," said Ding Duo, director of the Research Center for International and Regional Issues at the National Institute for South China Sea Studies.

A Philippine plane warned a Chinese military helicopter over the South China Sea that it was "flying too close," as tension between the U.S. ally and Beijing soars.