Three Nobel Prize laureates were among thousands of people who signed a petition urging European leaders to secure the release of a hunger-striking Ukrainian pilot from a Russian jail.
The 34-year-old Nadiya Savchenko is standing trial for alleged involvement in the death of two Russian journalists in war-torn Ukraine. She faces up to 23 years in prison if convicted.
Savchenko has denied all charges and has not been eating or drinking since her hearing was adjourned Thursday before she was given a chance to make her final statement.
Her case is seen by many Ukrainians as a symbol of resistance against what Kiev's pro-Western leaders view as Russia's aggression in the eastern industrial heartland of the former Soviet state.
Hundreds of demonstrators rallied yesterday outside Moscow's diplomatic mission in Kiev to demand her repatriation to Ukraine. The protests saw the Russian embassy pelted with eggs and the windows of at least one diplomatic car smashed.
Savchenko's fate has also sparked concern among Western governments and leading human rights figures.
The Belarussian writer Svetlana Alexievich and two other Nobel Prize winners in literature - Austria's Elfriede Jelinek and the Lithuanian-American Tomas Venclova - told European leaders that Savchenko's life and the bloc's credibility were at stake.
"Our ability to save her life will test the effectiveness of international diplomacy and our commitment to European values," said an open letter posted on the Internet yesterday and signed by more than 5,000 people by early today.
Savchenko was "kidnapped and imprisoned for more than twenty months in the Russian Federation," the letter said.
"The Russian authorities have made a mockery of civil rights, international law, and their own Constitution. They show disdain for the international community and the Minsk Protocol" that aims to bring an end to the 23-month war.
Russian prosecutors argue that Savchenko was involved in the killing of two Russian journalists in eastern Ukraine in 2014 in her capacity as a volunteer in a Ukrainian battalion.
She denies any involvement and says she was kidnapped and smuggled into Russia.
Her supporters are concerned that by refusing to drink water she may damage her health irreparably or not live long enough to attend the next hearing set for Wednesday.
The separatist war has claimed more than 9,100 live since pro-Russian insurgents angered by the ouster of Ukraine's Moscow-backed leadership revolted against the Kiev authorities in April 2014.
Russia rejects Ukrainian and Western charges of instigating and backing the unrest.
