Environmental activists in Manila, Philippines, display placards and mock missiles as they picket the Chinese Consulate to protest alleged military build-up by China on South China Sea. Pic/AP

Washington/Beijing: In a stern warning to China, the US has vowed to "protect its interests" in the disputed South China Sea and defend international territories from being taken over by "one country". This evoked an angry response from Beijing, which claimed "indisputable sovereignty" over the region.