Medical tests on a jailed Ukrainian pilot on hunger strike show her blood is thickening, putting her at risk of developing a blood clot which could kill her, her lawyers said Monday. 

Nadiya Savchenko was convicted last month over the killing of two Russian journalists in eastern Ukraine and sentenced to 22 years in a Russian prison. 

The 34-year-old military pilot denies any involvement in the shelling death of two Russian state television reporters.

Last Wednesday, she began a dry hunger strike, refusing both food and water, to protest her sentence and demand her immediate return to Ukraine.

Her lawyers sounded the alarm on Monday, saying tests showed her blood was becoming very thick and she faced the risk of dying from a blood clot.

"As doctors told her, her blood has turned into tar, which is very difficult for her heart to pump through," one of her lawyers, Nikolai Polozov, said on Facebook after seeing her earlier in the day.

"There's a possibility she may develop a blood clot and die suddenly, literally in her sleep," he added.

After test results showed her health was worsening, Russian prison officials threatened to start force-feeding her and offered to put her in hospital, which she refused. 

But she agreed to be put on a drip and receive glucose and sodium chloride intravenously, Polozov said.

In a statement, Russia's prison administration on Monday said Savchenko was in "stable" condition and had agreed to receive "supporting treatment".

Polozov said Savchenko had no immediate plans to start taking food and water again, saying she was "hanging in there" but her strength was failing. 

He was expected to visit her again on Thursday -- the same day as President Vladimir Putin is to hold his annual televised call-in show, with Savchenko urging her supporters to quiz him on when she will be returned to her native Ukraine.

Savchenko has staged several hunger strikes during the past, including during her high-profile trial.

In Ukraine, she has become a symbol of resistance against what Kiev says is Moscow's aggression and has been elected to parliament in absentia.