Protesters shout slogans during a rally near the golf course where the Terminal High Altitude Area Defense (THAAD) system will be deployed in Seongju, South Korea, March 15, 2017. About 200 local residents attended the rally on Wednesday to protest against the deployment of THAAD system. (Xinhua/Liu Yun)

SEOUL, May 30 (Xinhua) -- South Korean President Moon Jae-in on Tuesday ordered an investigation into the unauthorized delivery of four more mobile launchers of the U.S. missile shield to the country.

Yoon Young-chan, chief presidential press secretary, told a press briefing that President Moon said it was "very shocking" after he was briefed by his top national security advisor Chung Eui-yong on the unauthorized delivery.

About two weeks before the May 9 presidential by-election, two mobile launchers and a radar for the U.S. Terminal High Altitude Area Defense (THAAD) missile interception system were transported in the middle of night to a golf course at Soseong-ri village in Seongju county, North Gyeongsang province.

THAAD is composed of six mobile launchers, 48 interceptors, a AN/TPY-2 radar and a fire and control unit.