LONDON (AP) — More than 100 Russian doctors signed an open letter published Saturday that demands the immediate release of an artist and musician who was sentenced to seven years in prison for swapping supermarket price tags with antiwar messages.

The letter calling for Sasha Skochilenko to be freed was addressed to Russian President Vladimir Putin and warned that time in prison could lead to a “significant deterioration” in the 33-year-old artist's health.

Skochilenko was “diagnosed with a number of severe chronic diseases that require proper medical supervision and a special diet,” states the letter, which goes on to note the doctors’ indignation at the “obvious injustice of the verdict.”

A Russian court sentenced Skochilenko on Thursday. She was arrested in her native St. Petersburg in April 2022 and charged with spreading false information about the military with her messages opposing the war in Ukraine.

“The Russian army bombed an arts school in Mariupol. Some 400 people were hiding in it from the shelling,” one replaced price tag read. Another said, “Russian conscripts are being sent to Ukraine. Lives of our children are the price of this war.”

A customer at the supermarket who found the slogans reported them to authorities. Skochilenko did not deny but rejected the accusation of spreading knowingly false information.

Skochilenko’s arrest came about a month after authorities adopted a law effectively criminalizing any public expression about the war that deviates from the official Kremlin line. The legislation has been used in a widespread crackdown on opposition politicians, human rights activists and ordinary citizens critical of the Kremlin, with many receiving lengthy prison terms.

Because Skochilenko was in custody for nearly 19 months before her trial, her seven-year sentence will be reduced by more than two years since every day served in a pre-trial detention center counts as 1.5 days of time served in a regular penal colony.

But she has struggled while in custody due to health problems that include a congenital heart defect, bipolar disorder and celiac disease, her lawyers and partner have said.

Russia’s most prominent human rights group, Memorial, a co-winner of the 2022 Nobel Peace Prize, has declared Skochilenko a political prisoner.

According to OVD-Info, a rights group that monitors political arrests and provides legal aid, a total of 19,834 Russians were arrested between Feb. 24 2022, when the war in Ukraine began, and late October of this year for speaking out or demonstrating against the war.