Kim Keon-hee, the wife of South Korea's ousted president Yoon Suk-yeol, has been indicted on bribery and other charges, a special prosecution team said on Friday, amid a widening probe into the country's martial law crisis and scandals involving the once powerful couple.

Following the indictment, Kim said she was sorry for causing concern and would further cooperate with further investigations.

Both Yoon and Kim have been arrested and are in jail, with Yoon already undergoing trial on charges that include insurrection following his ouster in April over a botched bid to impose martial law in December.

The couple are under separate investigations by special prosecutors appointed after Yoon's removal from office and President Lee Jae-myung took office.

It is the first time that a former first lady has been indicted in South Korea.

The charges against Kim, which are punishable by years in prison if she is found guilty, range from stock fraud to bribery that have implicated business owners, religious figures and a political power broker.

The former first lady has been the subject of numerous high-profile scandals, some dating back more than 15 years, which overshadowed Yoon's turbulent presidency and inflicted political damage on him and his conservative party.

Kim's lawyers have denied the allegations against her and said news reports about some of the gifts she allegedly received were groundless speculation.

On Friday, special prosecutors investigating the country's martial law crisis also indicted former Prime Minister Han Duck-soo, who was appointed by Yoon, on charges of abetting insurrection and committing perjury, a prosecution spokesperson said. (Reuters)