A bodyguard for President Park Geun-hye appeared at the Constitutional Court Thursday to face questioning over an influence-peddling scandal involving Park and her friend.

Lee Young-sun, an employee of the presidential security service, was summoned to testify at the fourth hearing of Park's impeachment trial following revelations he ran errands for the friend, Choi Soon-sil.

He refused to answer most questions by the parliamentary impeachment panel, but admitted to regularly visiting a dressmaker's shop to pick up the president's clothes on behalf of Choi.

He also said he was aware that Park and Choi were "acquainted."

Choi is accused of abusing her ties to the president to extort money from conglomerates, meddle in state affairs and win personal favors. Park was impeached by the parliament on Dec. 9 on suspicion of colluding with Choi and neglecting her duty during a deadly ferry sinking in 2014.

Expressing frustration at Lee's refusal to testify, Justice Kang Il-won, the chief justice for the case, reminded him of his obligation to speak unless the question involves issues related to national security or national secrets.

Kang pointed out that questions regarding the number of times Choi visited the presidential office does not involve national security.

Lee also responded to questions about Park's whereabouts during the ferry disaster that left more than 300 people dead or missing.

Critics have long argued that more lives could have been saved had she responded properly in the early hours of the sinking. Park insists she received briefings and gave orders by phone from her office at her residence.

The court has until early June to decide whether to uphold or reject the impeachment motion. (Yonhap)