More than 22,000 people have signed a petition asking Russian President Vladimir Putin to secure the release of Svetlana Davydova, a 36-year-old mother of seven who is accused of treason, from pretrial detention.
The petition, published on the website of the newspaper Novaya Gazeta, says Davydova should be allowed "to return home to her children," including an infant it says she had been breast-feeding.
The Russian children's ombudsman, Pavel Astakhov, said on Ekho Moskvy radio that the authorties involved in Davydova's should take into consideration the need of her children for their mother.
Davydova has been in a detention cell since being taken into custody in late January in the town of Vyazma.
She could be sentenced to 20 years in prison if tried and convicted of treason.
Davydova's husband, Anatoly Gorlov, has said that his wife phoned the Ukrainian Embassy in Moscow in April and said that a military base near their home had emptied out, suggesting the soldiers may have been deployed to Ukraine.
Russia denies involvement in the conflict in eastern Ukraine, despite what Kyiv and NATO say is incontrovertible evidence Moscow has sent troops and weapons to separatists.
Based on reporting by Ekho Moskvy and Novaya Gazeta