South Korea's new liberal president on Tuesday, May 30 demanded an investigation into why his office wasn't told by defense officials about the arrival of several additional launchers for a contentious U.S. missile defense system meant to cope with North Korea's nuclear threats, The Associated Press reports.

Before taking office on May 10, Moon Jae-in vowed to review the system's deployment, which has infuriated both Pyongyang and Beijing, which considers the system's powerful radar a security threat. Many of Moon's supporters don't want the system, which U.S. President Donald Trump suggested Seoul should pay for.

On Tuesday, senior presidential adviser Yoon Young-chan said in a televised conference that Moon has discovered that four additional launchers for the Terminal High-Altitude Area Defense system have arrived in South Korea since the original two launchers were installed in April.

Yoon said that senior Defense Ministry officials didn't report the arrival of the additional launchers when it gave Moon's policy advisory committee a policy briefing after Moon's inauguration. Moon described it as "very shocking" that the additional THAAD parts arrived secretively, Yoon said.

Moon is now working with Cabinet members who were appointed by his conservative predecessor, Park Geun-hye, who was ousted from office in March over a massive corruption scandal. Moon has nominated some of his own Cabinet members but they haven't formally taken office. Moon was sworn in as Park's successor right after winning a May 9 by-election, and hasn't had the usual two-month transition period.

The Defense Ministry said it would issue a statement in response to Moon's investigation order.

A THAAD battery consists of six truck-mounted launchers that can fire up to 48 interceptor missiles, fire control and communication equipment, and a powerful X-band radar officially known as AN/TPY-2. The THAAD system was installed in the southeastern town of Seongju.