MOSCOW (AP) — A Moscow court refused Wednesday to release a Ukrainian military officer who has been on hunger strike in a Russian prison since mid-December and has become a national hero in Ukraine.

The case of 33-year-old Nadezhda Savchenko has attracted global attention in recent weeks as concerns rise about her health. Both the United States and the 28-nation European Union have urged Russia to release the woman who is seen as a symbol of heroic resistance in Ukraine and has been elected to parliament.

Savchenko has been in Russian custody since June on charges that she provided guidance for a mortar attack that killed two Russian journalists who were covering the war between Ukrainian troops and Russia-backed separatists in eastern Ukraine. At the time of the attack, she served with the Aidar volunteer battalion that fights alongside the government forces in eastern Ukraine.

The circumstances of her capture remain unclear. Russia's Investigative Committee alleges Savchenko crossed into Russia voluntarily and illegally, disguised as a refugee. But Savchenko says she was captured by the separatists in eastern Ukraine and spirited across the border into Russia.

Savchenko is widely lauded at home. She was well known even before her captivity because of her stint as a soldier in Iraq with a Ukrainian contingent and later as one of the nation's few female military pilots.

In the autumn after her capture, she was elected a member of the Ukrainian parliament and appointed a delegate to the Parliamentary Assembly of the Council of Europe, an arm of the continent's leading human rights body. The rejected appeal asked for her to be released in order to attend a PACE session.

PACE president Anne Brasseur said that "time is running out" to save Savchenko's life, and the Committee of Ministers of the Council of Europe adopted a decision calling for her urgent release.

EU foreign policy chief Federica Mogherini said in a statement Wednesday that after being on hunger strike for 82 days, Savchenko "faces permanent damage to her health, or death" and called again for her release on humanitarian grounds.

Russian officials, in their turn, have insisted that Savchenko is not in immediate danger and if there is a serious change in her condition, she would be sent to a civilian hospital. In her court appearance Wednesday, Savchenko, wearing a red-and-white sweater, appeared glum but not disabled.

In an interview with the Open Russia website this month, Savchenko said she has been consuming a compound that includes protein and lactose.

"I am taking this mixture so that my brain will be the last thing to break down. Only for this," she said.

Her sister, Vera Savchenko, told The Associated Press in Kiev Wednesday that Savchenko decided to continue her hunger strike until the 99th day.

"This is not done out of stubbornness," she added. "This is just the weapon she has deployed. She is standing up against the Kremlin."

Savchenko's case has been a contentious issue in the Ukrainian conflict and in Russia-West relations. Ukraine demands that she be considered a prisoner of war, which would nominally make her eligible for the prisoner exchange taking place in stops and starts under a stumbling internationally brokered peace agreement.

On Monday, the presidents of Ukraine, France and Germany appealed to Russian President Vladimir Putin to release Savchenko. Ukrainian President Petro Poroshenko said Wednesday he had written separately to Putin. But the Kremlin hasn't responded publicly yet.

Russia has insisted that Savchenko must face trial. Keeping her in custody also has given Russia leverage to repeatedly denounce Ukrainian forces as the killers of journalists.

Savchenko's sister said she was disappointed but unsurprised by Wednesday's court ruling.

"The whole world has come out in her support and yet they tell her: 'Lay down your arms, you cannot win. They have broken others, everybody else has given up,'" Vera Savchenko said, adding her sister won't give up. "She will hold on to the last and will be free."

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Raf Casert in Brussels, Peter Leonard in Kiev and Vladimir Isachenkov in Moscow contributed to this report.