Tents are set up in front of Gyeongbok Palace in central Seoul, Tuesday, for sit-in protests by opposition parties and a coalition of progressive civic groups demanding the immediate ouster of President Yoon Suk Yeol. Korea Times photo by Shim Hyun-chul

Jeon Ji-ye, 33, stayed up all night at a sit-in protest in front of Gyeongbok Palace in central Seoul, Saturday, after she heard the news about President Yoon Suk Yeol's surprise release from detention.

"This is a matter of our survival," the civic activist said Tuesday. "I believe Yoon Suk Yeol is a very dangerous president … If he comes back [to power], he will definitely try declaring martial law again. Since he failed once, he could actually wage war next time."

She returned with a tent on Monday and joined dozens of like-minded protesters who braved the early spring cold snap overnight, wrapped in tinfoil blankets.

Calling for Yoon's ouster over his Dec. 3 martial law declaration, dozens of pro-impeachment protesters have staged overnight rallies in central Seoul near the Constitutional Court, which is expected to rule this month on whether to uphold the National Assembly's impeachment motion against the president. The protests have intensified since Yoon was released from jail after a local court decided his detention was invalid due to technicalities.

Among the group was 52-year-old Oh Mi-sook from Pyeongtaek, Gyeonggi Province, who has remained at the tents since Sunday night and participated in nearly every impeachment protest since last December.

"This is the only thing I can do — coming to the protest and hopefully inspiring others to join. It's nothing grand, but it's something I can do," she said.

"Many of us are out here, holding rallies every evening, just like how we fought these past three months in Yeouido, Namtaeryeong and Hannam-dong," Jeon explained, referring to past protest venues throughout the political turmoil. "I hope more people will join after they see us."

Jeon Ji-ye, leader of a civic group called Peace Power, stages an overnight sit-in protest at her tent near Gyeongbok Palace in Seoul, Tuesday, demanding President Yoon Suk Yeol's ouster. Korea Times photo by Shim Hyun-chul

The tents by individual protesters were joined by those set up by five opposition parties and a coalition of 1,700 progressive civic groups, which have been staging protests every evening since last week to the west of the palace's main gate. Some members have gone further, holding days-long hunger strikes and participating in overnight rallies.

Jeon and Oh said the idea of Yoon returning to office is both unimaginable and unacceptable. They are determined to remain at the sit-in until the final ruling by the Constitutional Court, despite the absence of a set date for the verdict.

The Korean Confederation of Trade Unions, Korea's major umbrella union, decided to join the overnight rallies starting Tuesday.

Meanwhile, on the opposite side of the palace, near the Constitutional Court, people supporting Yoon have been camping out for their own rallies.

Supporters of embattled President Yoon Suk Yeol participate in a rally near the Constitutional Court in Seoul, Tuesday, urging the court to overturn the impeachment motion passed at the National Assembly. Korea Times photo by Shim Hyun-chul

According to news reports and witnesses, around 100 protesters opposing Yoon's impeachment held overnight rallies beginning Monday. When this reporter visited the area early in the morning, most were gone, while a group of 50 people staged a relay of one-person protests in front of the Constitutional Court.

"Release the president! Investigate the election fraud!" a speaker shouted on stage during a pro-Yoon rally near Anguk Station.

Like many other rally participants, he claimed that Yoon "has no choice but to declare emergency martial law to protect the people of the free Republic of Korea" and referenced narratives about election fraud spread by far-right YouTubers.

Dozens of participants, most of whom are over 60, waved Korean and U.S. national flags along with "Stop the Steal" banners in response.

"News reporters, get out! You all make fake news!" a middle-aged woman wearing a mask and sunglasses shouted when approached for an interview. Many other protesters also declined to comment and expressed hostility toward passersby, while some were seen dozing off under the spring sun.

A supporter of embattled President Yoon Suk Yeol dozes off during a rally near the Constitutional Court in Seoul to demand the court overturn his impeachment, Tuesday. Korea Times photo by Shim Hyun-chul

According to volunteers who served hot tea and cup noodles at the protest venue, the overnight rally participants had since returned home.

Led by the outspoken conservative pastor Jeon Kwang-hoon of Sarang Jeil Church, the pro-Yoon bloc plans to stage protests there daily until the final verdict is announced. Meanwhile, the ultra-conservative Liberty Korea Party has been holding its own protests near the presidential residence in Hannam-dong.