Kim Keon Hee, the wife of South Korea's ousted former President Yoon Suk Yeol, has been indicted for 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, Reuters reported.

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 face separate investigations by special prosecutors appointed after Yoon's removal from office and since liberal President Lee Jae Myung took office in early June.

Following the indictment, Kim apologised for causing concerns and said she would make "no excuses" and face trial, according to Reuters.