Thousands of South Koreans have gathered for rival demonstrations in the capital Seoul, either demanding the arrest of President Yoon Suk Yeol over his failed December 3 martial law decree or calling for his impeachment to be declared invalid.

Yoon was brought into custody about three hours after hundreds of law enforcement officers entered the residential compound in their second attempt to detain him.

South Korea's Presidential Security Service chief resigned Friday and acting President Choi Sang-mok accepted it. President Yoon Suk Yeol remains in his fortified residence as law enforcement seeks to arrest him.

In a statement before his detention, the president said the ‘rule of law has completely collapsed in this country’.

Yoon’s detention, after a tense standoff outside the presidential residence, marks the latest chapter in a bewildering series of events since his martial law decree.

Impeached South Korean President Yoon Suk Yeol was detained by police at his residence Wednesday morning for questioning over his short-lived martial law attempt.

South Korea's impeached President Yoon Suk Yeol said the rule of law in the country had "completely collapsed" as he was detained in a massive law enforcement operation at the presidential compound on Wednesday morning.