Moscow (AFP) - A Ukrainian airforce pilot who has been on hunger strike in a Russian jail for 81 days might be transferred to a civilian hospital if her health deteriorates, the prison service said Tuesday.

The statement by Russia's prison service raised the possibility of Nadia Savchenko, who is also a member of the Ukraine parliament, being transferred from the hospital of a Moscow prison where she has been held for nearly nine months.

Speaking later in the day, one of her lawyers said she may stop the hunger strike if her health sharply worsens.

The 33-year-old helicopter navigator has been charged with involvement in the deaths of two Russian reporters in a mortar attack in east Ukraine.

She denies the charges, saying she was kidnapped and brought to Russia. In protest of the detention she launched a hunger strike on December 13.

"As soon as we see that there are serious complications we will request that civilian medical institutions take her and treat her," first deputy chief of the prison service, Anatoly Rudy, told Russian reporters.

He insisted that as of now Savchenko's condition was stable. The prison service confirmed his comment.

Human rights activists and lawyers, however, have sounded the alarm, with the Kremlin's rights council urging the Investigative Committee to allow the pilot's release from jail on humanitarian grounds.

Yelena Masyuk, a member of the council, said late last week that Savchenko could "die within days."

On Tuesday, one of the Ukrainian woman's lawyers said she had promised him to stop refusing food if she felt worse.

"I have obtained a promise from her that if things become completely awful she will listen and stop," Mark Feigin said on Twitter. "That's what she said."

Few had expected Savchenko, who has described herself as "very stubborn," to relent and end her strike.

In a phone call with President Vladimir Putin late Monday, Ukrainian President Petro Poroshenko, German Chancellor Angela Merkel and French leader Francois Hollande urged the pilot's release.

Earlier Monday, Poroshenko bestowed on Savchenko the country's highest honour, Hero of Ukraine, saying she was a "symbol of the invincibility of the Ukrainian spirit and heroism."

Putin's spokesman Dmitry Peskov declined to comment on Savchenko, referring all inquiries to the Investigative Committee.