South Korean President Yoon Suk Yeol's term in office has been dogged by personal scandals, an unyielding opposition and rifts within his own party, and a rapid fall from grace over his short-lived declaration of martial law last month.

South Korea's anti-corruption agency says impeached President Yoon Suk Yeol has been detained several hours after hundreds of the agency's investigators and police officers arrived at his presidential compound to apprehend him.

TOKYO (Kyodo) -- Japan is monitoring developments in South Korea with "particular and grave" concerns, the top government spokesman said Wednesday, following the detention of President Yoon Suk Yeol over his declaration of martial law in December.