The Ukrainian Justice Ministry has asked Moscow to extradite Ukrainian prisoners Stanislav Klykh and Nikolai Karpyuk, the Interfax news agency reported Thursday.
The men were jailed by a Russian court in the Chechen capital of Grozny in May 2016 after they were found guilty of fighting against Russian troops during the First Chechen War in the 1990s.
Klykh was given a 20-year prison term in a strict-regime penal colony, while Karpyuk received 22 years and six months.
Ukraine's First Deputy Justice Minister Natalya Sevostyanova told journalists that the request had been made on Thursday.
"While we've had no reaction from the Russian Federation, we expect that the problem can now be solved at a political level,” Sevostyanova said.
Both Karpyuk and Klykh denied the accusations and claimed that they had never visited Chechnya before the start of their trial, their lawyers said.
The pair are believed to belong to Ukrainian ultra-right organization UNA-UNSO, an extremist group banned in Russia.