With an arrest warrant against Yoon for alleged insurrection expiring at midnight (1500 GMT) on Monday, multiple groups held demonstrations near his official residence, some urging his immediate arrest and others protesting against it.
Yoon became the country's first sitting president to face arrest over his botched attempt to declare martial law on December 3, which triggered political chaos engulfing Asia's fourth-largest economy and a key US ally.
Protesters have gathered in downtown Seoul, where temperatures fell below minus 5C. (AP PHOTO)
The conservative president was impeached by parliament and is suspended from official duties while a court decides whether to reinstate or remove him.
On Friday, criminal investigators were blocked from arresting him by Yoon's presidential security service and military troops in a six-hour stand-off.
The Seoul Western District Court on Sunday rejected a complaint from Yoon's lawyers that the arrest warrant was illegal and invalid, Yonhap news agency reported.
Calls to the court seeking comment went unanswered.
Yoon's lawyers have said the warrant was unconstitutional because the Corruption Investigation Office for High-Ranking Officials (CIO), which leads his criminal investigation, has no authority under South Korean law to investigate any case involving insurrection allegations.
The lawyers said in a statement on Sunday they would report CIO chief Oh Dong-woon and the investigation team to prosecutors for what they called illegally executing the warrant, including by mobilising police when the anti-graft body has no authority to do so.
President Yoon Suk-yeol was impeached by parliament and is suspended from official duties. (AP PHOTO)
The CIO did not immediately respond to a request for comment.
"Judging the legitimacy of any legal interpretation and execution is difficult," Seok Dong-hyeon, a lawyer advising Yoon, said on Facebook.
"If there is an error in the legality of law enforcement against the incumbent president, it will be a big problem."
Some of Sunday's protesters had gathered overnight in downtown Seoul, where temperatures fell below minus 5C.
More than 5cm of snow piled up in parts of the capital, which was under a heavy snow warning.
"We have to re-establish the foundation of our society by punishing the president who has denied the constitution," said Yang Kyung-soo, leader of the Korean Confederation of Trade Unions (KCTU), a major labour group that participated in the protests.
"We must bring down the criminal Yoon Suk-yeol and arrest and detain him as soon as possible."
Impeached President Yoon Suk-yeol's supporters gathered near the presidential residence in Seoul. (AP PHOTO)
Nearby, Yoon supporters held placards reading "We will fight for President Yoon Suk-yeol" and "Stop the Steal", a phrase popularised by US President-elect Donald Trump's supporters after he lost the 2020 election.
Similar rallies drew tens of thousands on Saturday, prompting police to try to disperse union protesters occupying roads and disrupting traffic.
Two were detained, accused of assaulting police officers, Yonhap news agency reported.
On Saturday, the Corruption Investigation Office for High-Ranking Officials, which leads Yoon's criminal investigation, again asked acting President Choi Sang-mok, the finance minister, to order the security service to comply with the arrest warrant.
A finance ministry spokesperson declined to comment.
