"Oleh ended up in a punishment cell right after he was transferred to the colony," he said.
Sentsov's lawyer Dmitry Dinze has so far refrained from commenting on the reasons for his client's confinement in the punishment cell.
As reported, Sentsov is serving a sentence in the maximum security labor camp in the Yamalo-Nenets Autonomous District. This prison's inmates are serving sentences for commission of grave and especially grave crimes.
Earlier, Sentsov was detained by the Russian FSB Security Service in Russian-occupied Crimea in 2014 together with activist Oleksandr Kolchenko. They were brought to Russia and tried in a trumped-up case on charges of organizing acts of terror and arson on the peninsula. On Aug. 25, 2015, Sentsov and Kolchenko were sentenced to 20 years' and 10 years' in prison, respectively. On Oct. 21, 2016, Russia refused to extradite the two Ukrainians to Ukraine, claiming they had automatically acquired Russian citizenship after the annexation of Crimea.