The security chief of impeached South Korean President Yoon Suk Yeol said on Friday that he had been unfairly treated for a sitting leader and warned bloodshed must be avoided.

Yoon faces arrest over a criminal probe into his December 3 martial law bid.

Park Chong-jun, head of the Presidential Security Service (PSS), is himself under investigation for obstructing official duty related to a six-hour standoff last week with investigators trying to execute an arrest warrant for Yoon.

Arriving at police headquarters for questioning, Park, who is a former senior police official, said the current attempt to arrest a sitting president was wrong and Yoon deserved treatment "becoming of" the country's status.

"I believe there should not be any physical clash or bloodshed under any circumstances," Park told reporters, adding acting President Choi Sang-mok had not responded to his request for safety assurances for officials involved.

Hundreds of PSS agents blockaded the presidential compound and thwarted investigators from trying to arrest Yoon. The investigators were pulled back because of the risk of a clash.

Officials of the Corruption Investigation Office for High-ranking Officials (CIO), which is leading the investigation, have said PSS agents were carrying firearms during the standoff although no weapons were drawn.

The investigators obtained a new arrest warrant this week after the embattled leader defied repeated summons to appear for questioning.

On Thursday, lawyers for Yoon said the arrest warrant was illegal and invalid.

Yoon is under a separate Constitutional Court trial reviewing parliament's impeachment of the suspended leader on December 14 to decide whether to remove him from office permanently or reinstate him. (Reuters)