SEOUL - South Korea's ruling Democratic Party has planned to push for parliamentary hearing on the unauthorized delivery of four more mobile launchers of the US missile shield to the country, which failed to be reported to President Moon Jae-in.

The party's special committee on THAAD (Terminal High Altitude Area Defense) on Thursday told a press briefing in the National Assembly building that the defense ministry omitted "on purpose" the bring-in report of additional THAAD elements to President Moon.

The committee described the report omission as "mutiny" and the "loosened state discipline," announcing its plan to push for the parliamentary hearings.

Senior presidential press secretary Yoon Young-chan told a press conference Wednesday that the defense ministry intentionally omitted the report on the delivery of four more THAAD launchers to the country, following a probe into several defense ministry officials.

On Tuesday, President Moon ordered a thorough investigation into the unauthorized transportation as it failed to be reported to the new president who took office on May 10.

According to the presidential Blue House's investigation into military officers, working-level officials of the defense ministry included the four more launchers delivered to an unidentified US base in South Korea in the document, but those were omitted in the final version to report to Chung Eui-yong, top presidential national security advisor.

Moon said it was "very shocking" as the THAAD transportation, which profoundly affects the fate of people and the country, was not made public.

In addition, the intentional omission of the report to the Blue House came ahead of the South Korea-US summit meeting scheduled for late June.

About two weeks before the May 9 presidential by-election, the first THAAD elements such as the radar and two mobile launchers 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, the AN/TPY-2 radar and the fire and control unit.

The clandestine transportation raised speculation that it was aimed to politicize security issues during the election campaign period, which tended to benefit conservative candidates in the past elections.