According to the Yonhap News Agency, parts of the system were delivered on Monday to the Osan Air Base in Pyeongtaek, 43 miles south of Seoul.
The THAAD system has a range of over 200 kilometers (125 miles) and is designed to intercept short, medium and intermediate ballistic missiles at the terminal incoming stage. The agreement on THAAD between South Korea and the United States was reached in July 2016, spurred by North Korea's nuclear program development.
Earlier, US Department of Defense spokesman Navy Commander Gary Ross told Sputnik that Missile launches by North Korea confirmed that the decision to deploy the THAAD system to South Korea was right.
On Monday, media reported that North Korea fired four ballistic missiles, and three landed in Japan's exclusive economic zone, triggering a negative reaction from, Seoul, Tokyo and their allies.