A former military commander was on Friday indicted on charges of power abuse and political meddling.
Prosecutors zeroed in on suspicions he masterminded a plan to impose martial law when then-President Park Geun-hye faced an impeachment trial in 2017.
Cho Hyun-chun, former head of the now-defunct Defence Security Command, DSC, is accused of instructing his subordinates to write up a report on elections at the Korea Freedom Federation, a major conservative group, in 2016, according to prosecutors.
Cho was also accused of having DSC agents stage rallies, run columns and advertisements supporting Park the same year, and embezzling 60 million won ($46,000) from the command.
The former military commander was placed under arrest in March shortly after he returned to the country from the United States which he had fled to avoid a probe in late 2017.
Prosecutors are expected to focus their investigation on the alleged martial law plan.
Cho is suspected of instructing a task force he formed in February 2017 to draw up a contingency plan based on an illegal declaration of martial law to crack down on candlelight protesters by force and reporting it to then Defence Minister Han Min-koo.
Months of street candlelight vigils led to the ouster of then-President Park at the time.
The martial law plan commissioned by Cho included mobilising 200 Army tanks, 550 armored vehicles, and more than 6,000 armed forces to form a martial law army.
Prosecutors are reviewing whether drawing up such a document constitutes conspiracy of a rebellion.
Yonhap/NAN
