Anti-Yoon Suk Yeol supporters stage a rally near Gyeongbok Palace in Seoul, Dec. 21. Yonhap

Massive rallies took place in downtown Seoul on Saturday either calling for the swift ouster of President Yoon Suk Yeol, or opposing it, over his martial law declaration.

A civic group demanding Yoon's immediate resignation held a rally near Gwanghwamun Square, which brought together at least 300,000 people, a count claimed by the group.

Holding K-pop light sticks, the protesters urged the authorities to immediately arrest Yoon for his shocking, albeit short-lived, declaration of martial law on Dec. 3, which led to the National Assembly's vote to impeach him last Saturday.

Yoon's presidential powers were suspended, but he remains in office pending a decision by the Constitutional Court.

Some 1 kilometer away from the protest venue, conservative groups launched a separate massive rally in support of Yoon.

Waving the South Korean and American flags, hundreds of thousands of the participants called for his reinstatement.

No clashes have been reported between the two sides, according to police officers.

Braving the cold, many across the country also took to the streets in protest of Yoon.

In the southwestern city of Gwangju, an association of 175 civic groups held a large-scale protest calling for Yoon's impeachment and the dismantlement of the ruling People Power Party. (Yonhap)

Pro-Yoon Suk Yeol supporters stage a rally near Gwanghwamun Square in Seoul, Dec. 21. Yonhap