Ukrainian activist Volodymyr Balukh, who is serving a five-year prison term in Russia on charges he and his supporters say are politically motivated, has been placed in solitary confinement.
The Crimean Rights Defense Group nongovernmental organization quoted Balukh's sister, Nadia, as saying that officials at the Correctional Colony No. 4 in the western Russian town of Torzhok had informed her on April 9 that her brother had been placed in solitary confinement for 15 days on April 4.
She said the colony guards refused to pass food and clothing parcels to Balukh, and told her that inmates placed in solitary confinement could not receive items from their relatives.
It is not clear why Balukh was placed in solitary confinement.
The 48-year-old activist was initially arrested in December 2016 in Russia-annexed Crimea. He was convicted on a weapons-and-explosives possession charge in August 2017.
His conviction and nearly four-year prison sentence were reversed on appeal and returned to a lower court, which issued the same verdict and sentence in January 2018.
A new case against Balukh was opened in March 2018, after the warden of the penal facility in Crimea where he was held sued him, claiming that Balukh attacked him.
In July, a court found Balukh guilty of the second charge and ruled that he will serve a total of five years in prison for both convictions.
In October, the top regional court reduced Balukh's five-year prison term by one month.
Russia seized Ukraine's Crimean Peninsula in March 2014, sending in troops and staging a referendum denounced as illegitimate by at least 100 countries, after Moscow-friendly Ukrainian President Viktor Yanukovych was pushed from power by protests.
Rights groups say that since then, Russia has moved aggressively to prosecute Ukrainian activists and anyone who questions the annexation.