"The question of [Yaroshenko's] removal from solitary confinement as well as the transfer to a different prison with improved conditions, remain open," the spokesperson said. "We are calling on the US authorities to expedite the process."
The spokesperson said they recently visited Yaroshenko in prison and he complained about his prolonged placement in solitary confinement for more than a month.
"[The prolonged solitary confinement] could not be beneficial to his health," the spokesperson said.
Yaroshenko was captured in Liberia in 2010 and handed over to the US authorities despite protests by Russia. A US court sentenced Yaroshenko to 20 years in 2011 on charges of conspiring to import cocaine into the United States.
In April, the Russian Embassy in the United States voiced concerns over reports about Yaroshenko being humiliated in prison, calling on the prison administration to stop violating his fundamental rights.