ST PETERSBURG (Reuters) - A Russian court handed down a prison sentence of nearly three years to Darya Kozyreva, a young activist who used 19th-century poetry and graffiti to protest the conflict in Ukraine.

A Reuters witness in the court on Friday said Kozyreva, 19, was found guilty of repeatedly "discrediting" the Russian army after she put up a poster with lines of Ukrainian verse on a public square and gave an interview to Sever.Realii, a Russian-language service of Radio Free Europe.

She pleaded not guilty, calling the case against her "one big fabrication," according to a trial transcript compiled by Mediazona, an independent news outlet.

She was sentenced to two years and eight months in prison.

Kozyreva is one of an estimated 234 people imprisoned in Russia for their anti-war position, according to a tally by Memorial, a Nobel Prize-winning Russian human rights group.

In December 2022, aged just 17, Kozyreva sprayed "Murderers, you bombed it. Judases" in black paint on a sculpture of two intertwined hearts, erected outside St Petersburg's Hermitage Museum and representing the city's links with Mariupol, a Ukrainian city largely razed to the ground during a siege that spring.

In early 2024, after being fined 30,000 roubles ($370) for posting about Ukraine online, Kozyreva was expelled from the medical faculty of St Petersburg State University.

A month later, on the conflict's two-year anniversary, she taped a piece of paper containing a fragment of verse by Taras Shevchenko, a father of modern Ukrainian literature, onto a statue of him in a St Petersburg park:

"Oh bury me, then rise ye up / And break your heavy chains / And water with the tyrants' blood / The freedom you have gained."

Kozyreva was swiftly arrested and held in pre-trial detention for nearly a year, until she was released this February to house arrest.

Addressing the court on Friday, Kozyreva said she believed she had committed no crime.

"I have no guilt, my conscience is clear," she said, according to Mediazona's transcript.

"Because the truth is never guilty."

($1 = 80.9000 roubles)

(Reporting by Reuters in St Petersburg and Mark Trevelyan and Lucy Papachristou in London; Writing by Lucy Papachristou; Editing by Emelia Sithole-Matarise)