By Hyun Young Yi and Jack Kim
SEOUL (Reuters) -South Korea's impeached President Yoon Suk Yeol told supporters in a letter he will "fight until the end" as he faces an attempt by authorities to arrest him over his short-lived imposition of martial law last month, a lawyer said on Thursday
It was unclear when and how police could make the arrest and 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 it.
On Thursday, police scuffled with Yoon supporters who laid down in the road to try to block access to his residence. Police issued dispersal orders and then forcibly removed some protesters, Reuters journalists said.
Yoon wrote in the letter late on Wednesday to the hundreds of supporters gathered near his official residence: "I am watching on YouTube live all the hard work you are doing."
"I will fight until the end to protect this country together with you," he said in the letter, an image of which was sent to Reuters by Seok Dong-hyeon, a lawyer advising Yoon.
The opposition Democratic Party, which has majority control of parliament and led the impeachment of Yoon on Dec. 14, said the letter proved Yoon was delusional and remains committed to complete his "insurrection".
"As if trying to stage insurrection wasn't enough, he is now inciting his supporters to an extreme clash," party spokesman Jo Seoung-lae said in a statement.
Yoon shocked the country with a late-night announcement on Dec. 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 and voted against Yoon's order. About six hours after his initial decree, Yoon rescinded it.
On Tuesday, a court approved a warrant for Yoon's arrest, which potentially would make him the first sitting president to be detained as part of investigations over allegations he masterminded insurrection by trying to impose martial law.
Insurrection is one of the few criminal charges from which a South Korean president does not have immunity.
The Corruption Investigation Office for High-ranking Officials (CIO), which is leading a joint team of investigators that include the police and prosecutors, has until Jan. 6 to execute the arrest warrant.
Yoon Kab-keun, a lawyer for the impeached president, has said the arrest warrant was illegal and invalid because the CIO did not have the authority under South Korean law to request a warrant.
The lawyer on Thursday warned that police officers would face arrest by "the presidential security service or any citizens" if they try to detain Yoon on behalf of the CIO, saying their authority is limited to crowd control and maintaining public order.
Separately, Yoon's trial on impeachment is being heard at the Constitutional Court. The court will hold the second hearing on Friday. Yoon has been suspended from presidential duties and Finance Minister Choi Sang-mok has taken over as acting president until the outcome of the trial.
If the court upholds the impeachment and Yoon is removed from office, a new presidential election will be held within 60 days.
The warrant for Yoon's arrest and also a search of his office and residence was issued after the conservative career prosecutor defied repeated summons by investigators to appear for questioning in the criminal investigation separate from the Constitutional Court trial.
A former defence minister who officials said recommended Yoon declare martial law has been indicted on charges of insurrection and will go on trial on Jan. 16. Some of the top military officers commanding the defence of the capital, Seoul, have also been indicted for their alleged involvement.