This combo photo shows US President Donald Trump (left) and the Republic of Korea's President Moon Jae-in. (PHOTOS / AP and AFP)

SEOUL – The Republic of Korea (ROK)'s foreign ministry on Thursday fired a diplomat who leaked the classified content of phone conversations between ROK President Moon Jae-in and US President Donald Trump earlier this month.

The lawmaker from the main opposition Liberty Korea Party disclosed the detailed description of the conversation, classified as a level-3 secret, at a press conference

The ministry's disciplinary committee meeting was held earlier in the day, deciding to fire the diplomat at the ROK embassy in Washington, according to local media reports.

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The diplomat leaked the detail of the confidential Moon-Trump phone conversation to Khang Hyo-shang, a lawmaker of the main conservative opposition Liberty Korea Party.

Khang disclosed the detailed description of the conversation, classified as a level-3 secret, at a press conference.

President Moon bluntly criticized the lawmaker and the opposition party for using the diplomatic secret as a source of political fights during the cabinet meeting on Wednesday.

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Trump would visit Seoul late June on his trip to Asia to attend the Group of 20 (G20) summit in Osaka, Japan, according to the ROK presidential Blue House.