KIEV (Reuters) - Ukrainian lawmaker Nadiya Savchenko began a hunger strike on Friday to protest her detention on charges of planning a coup against the government, less than two years after being welcomed home as a national hero.

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Savchenko, an ex-helicopter navigator who served time in a Russian jail as a prisoner of war, was detained in Kiev on Thursday. Authorities charged her with planning an attack on parliament using grenades and automatic weapons.

Since her return to Ukraine, Savchenko has been a frequent and outspoken critic of the administration in Kiev. She says the authorities set up the coup plot to discredit her, but she does not deny seeking to overthrow the government.

Speaking at a televised hearing to determine her status until a trial, Savchenko said she would protest her treatment the same way she did her imprisonment in Russia.

“I will go on a hunger strike from today and again show all the unbelievers,” she said. “I will show the Ukrainian people what a hero is.”

She wore a black t-shirt with a trident motif - a national symbol in Ukraine - similar to her outfit while standing trial in Russia.

Following lengthy testimony from the defendant and prosecutors, the court ruled to keep Savchenko in police custody for two months while the investigation continues.

Her defiance in the Russian court earned her the nickname of Ukraine’s “Joan of Arc” and at the time posters calling for her release were hung on Ukrainian streets, at airports and in the chamber of parliament.

But she has fallen out of favor since returning to Kiev in 2016 because of her outspoken manner and erratic behavior.

In 2016, President Petro Poroshenko conferred on Savchenko the country’s highest honor, “Hero of Ukraine.” But on Thursday he suggested her alleged coup plot was a Russia-led special operation to destabilize Ukraine.

“All this is another reminder that a large-scale hybrid war is being waged against Ukraine,” he said in a post on Facebook.