The United States says it has begun deploying a missile-defense system in South Korea, prompting a quick rebuke from Russia and China.
South Korea last year chose the U.S. Terminal High Altitude Area Defense (THAAD) system to help protect it against threats from North Korea.
Officials from South Korea have said the system is being installed solely for defensive purposes, but both China and Russia worry that the radar system will penetrate deep into their territories.
China will "definitely be taking necessary measures to safeguard our own security interest," Geng Shuang, a Chinese Foreign Ministry spokesman said on March 7. He did not specify what measures may be taken.
The Interfax news agency quoted Leonid Slutsky, chairman of the International Relations Committee of the Russian State Duma, as saying the defense system goes beyond deterring the North Korean threat to "undermining the strategic balance" of the Korean Peninsula.
The start of the deployment of the defense system came a day after North Korea test launched four ballistic missiles into the ocean near Japan.