Hundreds of thousands of South Koreans took to the streets Saturday as rallies for and against the impeached President Yoon Suk Yeol intensified over the upcoming Constitutional Court's decision on whether to dismiss him.

Yoon was impeached by lawmakers over his disastrous December 3 declaration of martial law, and the court last month held weeks of tense impeachment hearings to determine whether to formally remove him from office.

Despite experts predicting a verdict by mid-March, the Constitutional Court has yet to rule, making Yoon's case the longest deliberation in its history.

Conspiracy theories have since emerged, leading to a surge in speculation, with some suggesting the justices must be experiencing tense disagreements.

Main streets in central Seoul were filled with protesters for and against Yoon, carrying various political signs as well as South Korean national flags.

"I cannot accept this situation. It is infuriating that there has still been no formal dismissal," Kim Min-ji, a 25-year-old anti-Yoon protester, told AFP.

"What frustrates me the most is that by delaying a verdict on the clearly defined charge of insurrection, the court is giving time and strength to the forces that are complicit in Yoon's crime."

But supporters of Yoon, including extreme right-wing YouTubers and religious figures, argue that justice will only be served if Yoon is reinstated.

"President Yoon only exercised his right as a president, and it is absurd to perceive what he did as an act of insurrection," Park Jong-hwan, a 59-year-old Yoon supporter, told AFP.

"This country will be in a much better, stable place once he returns to the presidential office."

In addition to the impeachment verdict, Yoon faces a criminal trial on charges of insurrection for declaring martial law in December, making him the first sitting South Korean president to stand trial in a criminal case.

He was detained in a dawn raid in January on insurrection charges but was released in early March on procedural grounds.

Yoon's release from detention has appeared to invigorate his supporters.

At least six of the eight justices on the Constitutional Court must vote to remove Yoon. Otherwise, he will be reinstated.

As tensions rise and political divisions deepen, and to prevent violent clashes, police are prepared to mobilize "all available equipment" on the day of the verdict, according to a police report.

The force is also considering deploying special units to address potential bomb threats, it said.