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.

China's military said Tuesday it warned off and expelled a Philippine C-208 aircraft that had entered airspace over a South China Sea island. Tian Junli, spokesman for the People's Liberation Army's Southern Theater Command, said in a statement that the Philippine aircraft illegally entered airspace over Huangyan Island without China's permission.

Australia spotted three Chinese warships sailing near its coast as Beijing accused Canberra of sending a spy plane into its "territorial airspace" over the contested South China Sea. Newsweek has contacted the Australian and Chinese militaries for comment by email.