Prosecutors allege that war veteran-turned-lawmaker Nadiya Savchenko planned to attack parliament using grenades and automatic weapons acquired from pro-Russian separatists in the eastern conflict zone.
Ukraine's State Security Service on Thursday detained lawmaker Nadiya Savchenko, an ex-military helicopter navigator who became a national hero after being held in a Russian jail, on charges of planning a military-style coup.
Prosecutors allege that Savchenko, who became a lawmaker on her return from Russia, planned an attack on parliament using grenades and automatic weapons acquired from pro-Russian separatists in the eastern conflict zone.
Savchenko, who has been a frequent and outspoken critic of the current authorities, does not deny the allegations against her outright.
She says undercover agents seeking to discredit her had encouraged her to plan to overthrow the government and that she had played along to bring the authorities' schemes to public notice.
"This is not a terrorist act, this is a political provocation to make the authorities look ridiculous," she said at a briefing on Tuesday.
She was detained in parliament on Thursday after lawmakers voted to remove her parliamentary immunity from prosecution and granted General Prosecutor Yuriy Lutsenko's request to allow her to be taken into custody.
"The plan was to overthrow the constitutional system by carrying out terrorist attacks on Kiev's central government quarter ... using weapons received from the leaders of the so-called DNR," Lutsenko told MPs, referring to the separatists.
The accusations mark a fall from grace for Savchenko, whose steely defiance while on trial in Russia, including hunger strikes and showing a judge the middle finger live on TV, earned her the nickname of Ukraine's "Joan of Arc".
She returned in May 2016 to great fanfare after a prisoner exchange with Russia, but quickly became a fiery and unpredictable opposition figure in parliament.
Ahead of Thursday's vote, Lutsenko presented the prosecutors' case against Savchenko, including undercover video clips that appeared to show her trying to persuade members of the Ukrainian military to join a plot.
With an aviator-style fleece-lined coat slung around her shoulders, Savchenko stood through the presentation arms-crossed, occasionally responding to the accusations with a derisive smile.
In a speech to lawmakers, she did not address the case against her directly, but accused the authorities of betraying the ideals of the 2013/2014 pro-European uprising.
If the status quo remains unchanged, "then the danger in parliament won't be me, your danger will be your people," she said.
"To accuse me of treason against Ukraine ... and to make anti-heroes out of yesterday's heroes simply because they do not agree with the policies and positions of the current government, that's all the authorities can do," she said.
Prosecutors say Savchenko's plot included working with prisoner exchange negotiator Volodymyr Ruban, who on March 9 was detained at a frontline checkpoint with a collection of weapons, including machine guns and explosives.
Ruban, who remains in detention, denies allegations he was planning an attack.
Savchenko was captured on the frontline in eastern Ukraine by pro-Russian separatists in 2014 and held in jail in Russia on murder charges that she said were fabricated. She became a symbol of resistance against Russia to many Ukrainians.
Since her return she has held talks with the separatists without the government's consent and published secret lists of people who were captured or are missing in the conflict.