Investigations and arrests continue after South Korean disgraced ex-President Yoon Suk-yeol’s failed bid to impose martial law.

A former South Korean prime minister and the country’s one-time spy chief have been arrested in connection with the short-lived imposition of martial law by former President Yoon Suk-yeol in December 2024, local media report.

In separate arrests, former Prime Minister Hwang Kyo-ahn was detained on Wednesday on charges of inciting an insurrection, and Cho Tae-yong, the former head of the National Intelligence Service (NIS), was taken into custody for several violations of NIS law, including dereliction of duty, South Korea’s Yonhap news agency reports.

According to Yonhap, Hwang posted on Facebook following the declaration of martial law, calling for the arrest of the country’s National Assembly speaker and for the eradication of those involved in alleged electoral fraud.

Former intelligence chief Cho, once a close confidant of disgraced President Yoon, is accused of knowing and failing to report plans for the imposition of martial law to the country’s National Assembly.

“The NIS Act obliges its director to report to the National Assembly, as well as to the president, if a situation that has a significant impact on national security arises,” Yonhap reported.

Prosecutors said that Cho, a career diplomat, failed to report on plans for martial law, despite “understanding its illegality”. At a hearing on Tuesday, Cho denied all of the charges against him, Yonhap said.

Hwang and Cho’s arrests come after prosecutors on Monday added another indictment against the former 64-year-old president Yoon, who was removed from office in April, and is now detained while awaiting trial for his failed attempt to impose martial law.

The latest indictment accuses the former president of attempting to provoke a military conflict between South Korea and North Korea by covertly sending drones into North Korea in an effort to legitimise the state of martial law he declared.

Prosecutors argue that the drone deployment over North Korea in October 2024 led to the leak of military secrets when one of the unmanned aerial vehicles crashed near North Korea’s capital, Pyongyang, Yonhap added.

State Prosecutor Park Ji-young told reporters that the special counsel team had “filed charges of benefitting the enemy in general and of abuse of power” against the former president.

Yoon’s move to impose martial law plunged South Korea into political crisis after armed soldiers were sent to parliament in a bid to stop lawmakers rallying against and outlawing his martial law bid. Yoon’s bid to seize power failed, and he was detained in January, becoming South Korea’s first sitting president to be taken into custody.

Yoon’s wife, Kim Keon Hee, is also in custody and standing trial on corruption charges, including stock manipulation, marking the first time a former first couple has been detained simultaneously.