North Korea fires unidentified projectile from near missile base - South Korea

Terminal High Altitude Area Defense (THAAD) interceptors arrive at Osan Air Base in Pyeongtaek, South Korea, in this handout picture provided by the United States Forces Korea (USFK) and released by Yonhap on March 7, 2017. USFK/Yonhap via REUTERS

SEOUL (Reuters) - The United States started to deploy the first elements of its advanced anti-missile defence system in South Korea on Tuesday after North Korea's test of four ballistic missiles, U.S. Pacific Command said, despite angry opposition from China.

The announcement came as North Korean state media said leader Kim Jong Un had personally supervised Monday's missile launches by an army unit that is positioned to strike U.S. bases in Japan, stepping up threats against Washington as U.S. troops conduct joint military exercises with South Korea.