Photo from flickr.com/Raffaella

"According to expert of the Regional Centre for Human Rights, lawyer Roman Martynovskiy, only for the period of the occupation of Crimea at least 2,200 detained citizens of Ukraine, 240 women among them, were moved in the correctional institutions of Russian Federation," the Crimean Human Rights Group said in its Crimean Human Rights Situation Review for October 2016.

They also reported two cases of Ukrainian citizens' death in prisons in Russia and Russia-occupied Crimea.

"A citizen of Ukraine, Valeriy Kerimov (born in Genichesk, Kherson region) died on September 8, 2016, in prison colony number 1 of the Republic of Adygea (Russia). He was transferred to a Russian prison colony from a detention facility of Crimea. He was sick with hepatitis and tuberculosis; he was not provided with medical assistance on time as a result of which he died," the review said.

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Human rights activists also mentioned another citizen of Ukraine Serhiy Glinyanik from Sevastopol, who died in Simferopol pre-detention center number 1 on August 30, 2016, due to lack of medical care.

Read alsoTrumped up case of "Ukrainian saboteurs" in Crimea"There are serious fears for the lives of the other two citizens of Ukraine. Yuriy Sayenko is in correctional institution No. 2 in Rostov-on-Don, and Leyla Huseynova is in a Simferopol pre-detention center. Both prisoners were found HIV and hepatitis; they are in urgent need of medical care," the Crimean Human Rights Group said.

The death in Adygea was also confirmed by Fiona Frazer, the head of the United Nations Human Rights Monitoring Mission in Ukraine, according to Krym SOS, a news portal about Crimea.