Berlin (AFP) - Berlin on Wednesday called for the immediate release of Ukrainian military pilot Nadiya Savchenko, saying her trial in Russia went against a peace deal aimed at ending a separatist war in Ukraine.

"The trial against Savchenko violates the spirit and letter of the Minsk agreement, we are therefore making a joint call with our partners for the immediate release of Nadiya Savchenko on humanitarian grounds," government spokesman Steffen Seibert said, referring to a clause in the accord that requires Ukraine and Russia to swap prisoners and hostages.

Germany was following the trial closely, Seibert said, underlining concerns over how Savchenko had been treated since her detention in June 2014.

Referring to Savchenko's hunger strike, Seibert said there were serious concerns over her health condition as well as over her imprisonment including solitary confinement, when she was also subjected to "questionable interrogation methods that violated international standards".

Savchenko, who announced her protest action in court last Thursday, is accused of involvement in the death of two Russian state television journalists in a mortar attack that occurred two months after revolt erupted in Ukraine's pro-Moscow east in April 2014.

The 34-year-old Iraq war veteran faces up to 23 years in prison if convicted in a case that has drawn global attention and been attended by Western monitors concerned about Russia's record on human rights.