SEOUL: South Korean authorities on Friday arrived at the residence of the impeached President Yoon Suk Yeol to arrest him with protesters gathering outside his residence, clashing with police and pledging to prevent his arrest. Yoon is under criminal investigation for insurrection over his short-lived martial law attempt on December 3. An arrest would be unprecedented for an incumbent South Korean president. Officials from the Corruption Investigation Office for High-ranking Officials (CIO), which is leading a joint team of investigators that include the police and prosecutors, had arrived gates of Yoon's compound shortly after 7am (2200 GMT Thursday), according to Reuters witnesses. Yonhap News Agency reported that about 3,000 police had been mobilised in preparation. It was unclear whether the Presidential Security Service, which has blocked access by investigators with a search warrant to Yoon's office and official residence, would try to stop the arrest. Media reports said the CIO vehicles did not immediately enter the compound. Protesters gathered in the pre-dawn hours near his residence, with the numbers swelling into the hundreds amid media reports that investigating authorities would soon try to execute the arrest warrant that was approved on Tuesday after Yoon refused summons to appear. "We have to block them with our lives," one was heard saying to others. About a dozen protesters tried to block a group of police officers at the entrance to a pedestrian overpass. Some chanted "President Yoon Suk Yeol will be protected by the people," and called for the head of the CIO to be arrested. Pyeong In-su, 74, said that the police had to be stopped by "patriotic citizens", a term Yoon used to describe those standing guard near his residence. Holding a flag of the United States and South Korea with the words "Let’s go together" in English and Korean, Pyeong said he hoped incoming US President Donald Trump would come to Yoon's aid. "I hope after Trump's inauguration he can use his influence to help our country get back on the right track," he said. Yoon sent shockwaves through the country with a late-night announcement on December 3 that he was imposing martial law to overcome political deadlock and root out "anti-state forces". Within hours, however, 190 lawmakers had defied the cordons of troops and police to vote against Yoon's order. About six hours after his initial decree, Yoon rescinded it. He later issued a defiant defence of his decision, saying domestic political opponents are sympathetic to North Korea and citing uncorroborated claims of election tampering. Insurrection is one of the few criminal charges from which a South Korean president does not have immunity. Yoon's lawyers have said the arrest warrant was illegal and invalid because the CIO did not have the authority under South Korean law to request a warrant. Yoon has been isolated since he was impeached and suspended from power on December 14. Separate from the criminal investigation, his impeachment case is currently before the Constitutional Court to decide whether to reinstate or permanently remove him. A second hearing in that case is scheduled for later on Friday.