SEOUL — South Korean investigators will seek an extension of a warrant to arrest impeached President Yoon Suk-yeol, an official said on Monday, as an anti-graft agency asked the police to take over efforts to execute the arrest of the embattled leader.

The requests came after a failed attempt to serve the warrant on Friday following a tense standoff with Presidential Security Service guards who formed a human chain to block access to Yoon by the investigators.

Yoon is under criminal investigation for insurrection over his Dec 3 martial law bid that stunned South Korea and led to the first arrest warrant to be issued by the court for a sitting president.

The Corruption Investigation Office for High-ranking Officials, or CIO, is leading a probe, joined by the police and the prosecutors' office, into allegations that Yoon masterminded insurrection with his imposition of martial law.

Yoon was impeached by parliament on Dec 14 and suspended from presidential duties. The Constitutional Court is trying the case to decide whether to remove him from office permanently or reinstate him.

The CIO sent a notice to the police requesting them to take over execution of the arrest warrant, the anti-corruption agency said in a statement to reporters.

The National Office of Investigation, or NOI, of the Korean National Police Agency said on Monday that the document sent by the CIO regarding the transfer of the execution of the arrest warrant for Yoon contained "legal flaws", making it difficult for the police to comply with.

The police believe the document is legally flawed, and the execution of the warrant should take place within the framework of the joint investigation unit, according to Youn Kun-young, a member of the Public Administration and Security Committee of South Korea's National Assembly.

The joint investigation unit consists of the CIO, the NOI and the defense ministry's investigation headquarters.

According to local media reports, the police's stand implies that the responsibility for executing the arrest warrant lies with CIO prosecutors, with the police playing a supporting role rather than serving as the main executor.

The NOI said the police are discussing methods for executing the arrest warrant within the framework of the joint investigation unit with the CIO, adding it is also considering measures to address potential obstruction by personnel from the Presidential Security Service.

Critics frustrated

The CIO's request comes amid frustration among Yoon's critics with the CIO for failing to carry out his arrest, which is due to expire at midnight on Monday.

Yoon's lawyers have argued that the anti-graft force leading his criminal investigation has no authority under South Korean law to investigate any case involving insurrection accusations.

On Monday, Seok Dong-hyeon, a lawyer advising Yoon, said the bid to transfer the execution of the arrest warrant is effectively an admission by the CIO that its probe and the warrant were "illegal".

After the failed attempt to execute the warrant, the CIO asked acting President Choi Sang-mok to direct the Presidential Security Service to cooperate with investigators. Choi has not reacted to that request.

The unprecedented attempt to arrest an incumbent president has intensified dueling rallies by those supporting Yoon, and those calling for Yoon's punishment.

On Monday, a group of Yoon supporters held a news conference and described the fight for Yoon as an "international battle" for freedom.

Amid the ongoing political upheaval, US Secretary of State Antony Blinken is visiting South Korea this week, according to the US State Department. His visit comes after Yoon's martial law declaration sent South Korea into political chaos, drawing rare rebuke from officials in Washington, including Blinken's deputy, Kurt Campbell, who said it was "badly misjudged".

Speaking after his meeting with South Korean Foreign Minister Cho Tae-yul, Blinken said Washington had expressed "serious concerns" to Seoul over some of the actions Yoon took over the course of his martial law declaration.

Agencies - Xinhua