Hundreds of supporters of South Korea's impeached President Yoon Suk Yeol rallied outside his home on Wednesday in a bid to protect him as investigators prepared a fresh arrest attempt.

Yoon has refused questioning and resisted arrest after his bungled 3 December martial law decree plunged South Korea into its worst political crisis in decades.

Investigators secured a new arrest warrant Tuesday after an initial seven-day order expired. Several hundred members of his base rushed to the conservative leader's house in central Seoul in response, braving sub-zero temperatures.

"A large number of people are coming out to join us. Despite the cold weather, many stayed up all night last night, braving the chill," Lee Hye-sook, a 57-year-old Yoon supporter, told AFP outside his residence.

"Witnessing their resilience against the wind and cold, I am confident that President Yoon Suk Yeol will return, and we will prevail."

Some supporters left flowers outside and ribbons with the Trump-style slogan "Make Korea Great Again!," while others waved American flags at the gates of the compound from where the suspended leader has resisted arrest.

You Se-ryung, a 46-year-old YouTuber camped outside, said key security ally the United States should intervene and "help" South Korea. Many of Yoon's supporters have adopted slogans used by US president-elect Donald Trump.

"Even if President Yoon Suk Yeol returns, whether or not the impeachment is overturned, I don't think this issue can be resolved within South Korea. That's why I brought out a Trump flag today," he told AFP.

Yoon's legal team said on Wednesday he remains inside his residential compound, after investigators cast doubt on his whereabouts a day earlier.

"Last night, I personally visited the official residence, met the president there, and left," said Yoon's lawyer Yoon Kap-keun, who is unrelated.

The Corruption Investigation Office (CIO), which is leading the probe into the president, has kept secret the duration of the second warrant it requested after an initial seven-day document expired on Monday.

Yoon would become the first sitting South Korean president to be arrested if investigators are able to detain him.

However, they would only have 48 hours to request another arrest warrant in order to keep him in detention or be forced to release him.

Barbed wire, barricade

An AFP journalist saw Yoon's guards walking behind rows of buses and locked entrance gates covered in barbed wire at the residential compound on Wednesday. 

CIO chief Oh Dong-woon said on Tuesday the force would "prepare thoroughly" to make sure their second arrest attempt was successful.

South Korea's Constitutional Court has slated January 14 for the start of Yoon's impeachment trial, which would proceed in his absence if he does not attend.

His legal team said he planned to attend the trial at some stage and lawyer Yoon Kap-keun told reporters on Wednesday "the President's position... remains unchanged."

"Of course, issues related to security and safety must be resolved in advance," he said.

National Assembly Speaker Woo Won-shik said it was distressing to watch Yoon mobilise force to stop his arrest because the "whole world" was watching.

"The president must no longer plunge the country into confusion and should engage in judicial procedures with a sense of responsibility," he wrote in a post on social media platform X.

Investigators are trying to work out how to again tackle an expected wall of security before that trial begins after being stopped by hundreds of Presidential Security Service (PSS) guards last week.

"The number of PSS personnel cannot be disclosed as it is confidential information," a service spokesperson told AFP.

A lawmaker from Yoon Suk Yeol's People Power Party, Yoon Sang-hyun, turned up with other MPs outside their leader's home on Wednesday to repudiate the warrant.

"I firmly believe that it is a clear violation of the law," he said.

The impeached Yoon is being investigated on charges of "insurrection" and, if formally arrested and convicted, faces prison or, at worst, the death penalty. 

The Constitutional Court has up to 180 days from 14 December, when it received the case, to determine whether to dismiss Yoon or restore his presidential powers.