Ukrainian President Petro Poroshenko has called on his Russian counterpart Vladimir Putin to release the jailed Ukrainian pilot Nadia Savchenko.
Poroshenko told Polish media on January 27 that he had sent a letter to Putin with the appeal.
Savchenko was captured by pro-Russian separatists in eastern Ukraine last June and transported to Russia.
She awaits trial for aiding in the killing of two Russian journalists during the conflict in eastern Ukraine, charges she denies.
To protest her detention, Savchenko has gone on hunger strike, now in its second month.
After her imprisonment in Russia, Savchenko was elected to the Ukrainian parliament in October.
The Parliamentary Assembly of the Council of Europe on January 26 also urged Russia to release her.
In a letter publicized on January 12, Savchenko vowed to continue her fight, writing her "spirit cannot be crushed."