The South Korean president says he was shocked to find that additional launchers had been introduced to the US anti-missile system without being reported to the new government or public.
South Korea's President Moon Jae-in has ordered an investigation after the defence ministry failed to inform him that four more launchers for the controversial US THAAD anti-missile system had been brought into the country, his spokesman said on Tuesday.
The Terminal High Altitude Area Defense (THAAD) system battery was initially deployed in March in the southeastern region of Seongju with just two of its six maximum-load launchers to counter a growing North Korean missile threat.
During his successful campaign for the May 9 presidential election, Moon called for a parliamentary review of the system, the deployment of which infuriated North Korea's lone major ally China.
"President Moon said it was very shocking" to hear that four additional launchers had been installed without being reported to the new government or to the public, presidential spokesman Yoon Young-chan said during a media briefing.
Moon had campaigned on a more moderate approach to Pyongyang, calling for engagement even as the reclusive state pursues nuclear weapons and ballistic missile programmes in defiance of UN Security Council resolutions and threats of more sanctions.
The US military in South Korea did not have an immediate comment in response to what Moon said. The South Korean military also did not immediately comment.
Improving ties with China
Moon's order of an investigation into the THAAD launchers came amid signs of easing tensions between major trading partners South Korea and China.
South Korea's Jeju Air said on Tuesday that China approved a plan to double flights to the Chinese city of Weihai from June 2.
China has been incensed over the THAAD deployment, fearing it could give the US military the capability of seeing into its own missile systems, and could open the door to a wider deployment of the system, possibly in Japan and elsewhere, military analysts say.