Anti-Yoon supporters urge the president's removal during a protest in Seoul, Feb. 1. Yonhap

Crowds of protesters gathered in central Seoul in massive rallies Saturday, either opposing the ouster of impeached President Yoon Suk Yeol or urging his removal from office, following his recent indictment with detention.

An estimated 3 million people, according to organizers, thronged Seoul's central Gwanghwamun area, waving the Taegeukgi and the Stars and Stripes and calling for Yoon's release in a rally opposing his impeachment.

Last Sunday, prosecutors indicted Yoon with detention on insurrection charges over his short-lived Dec. 3 declaration of martial law. The week after the declaration, the National Assembly voted to impeach Yoon, prompting a Constitutional Court trial to decide whether to reinstate or permanently remove him from office.

"Yoon Suk Yeol will be made to come back if 10 million people gather on March 1. (We) can change everything, whether it's the Constitution or anything else," said conservative activist pastor Jeon Kwang-hoon, who spearheaded the rally, referring to a mass gathering he is planning on that date.

The police's unofficial estimate of the participants was 38,000.

Pro-Yoon supporters wave Korean and U.S. flags during a protest in Seoul, Feb. 1. Yonhap

Similar rallies in support of Yoon were also held near the National Assembly in Seoul's western Yeouido district and in front of the Seoul Central District Court in southern Seoul.

Also in Gwanghwamun, a separate rally urged a Constitutional Court ruling to oust Yoon, with 100,000 participants according to organizers. The police estimated the number at 6,000.

Participants called for the "immediate removal" of Yoon, while also criticizing acting President Choi Sang-mok for vetoing a National Assembly bill calling for a special counsel investigation into Yoon over the martial law declaration.

"Let us completely end, with the power of the people, the insurrection scheme by the anti-Constitution forces, including Yoon Suk Yeol and the (ruling) People Power Party," said Kim Min Moon-jung, who spearheaded the rally against Yoon.

Some 240 traffic police personnel were mobilized in Seoul as the mass rallies caused traffic congestion and other inconveniences. (Yonhap)