South Korea's Ministry of Foreign Affairs has launched a probe into allegations that the country's top diplomat in Mongolia developed collusive ties with a visa broker and abused his authority by harassing subordinates.

According to the ministry on Tuesday, it obtained a transcript of the alleged broker mentioning encounters with Ambassador Chung Jae-nam while explaining the details of procuring a visa to South Korea, including associated costs and likelihood of obtaining the document.

Chung is suspected of colluding with the broker and illegally intervening in the South Korean government's visa application review process.

The Federation of Korean Trade Unions representing workers at overseas missions also requested the ministry probe allegations that Chung verbally abused embassy employees, including an incident where he screamed at employees while questioning the whereabouts of leftover food from an event in March.

The incident apparently led to Chung forcefully reassigning the employee in charge of the event.

The diplomat is also accused of misappropriating the embassy budget for personal expenditures.