Ukraine is marking the official Day of Remembrance of the Victims of the Holodomor, which commemorates the millions who died of famine under Soviet dictator Josef Stalin.
In central Kyiv on Saturday, President Petro Poroshenko and hundreds of other people laid symbolic wheat ears and lit candles before the monument commemorating victims of the famine.
"Today we commemorate the 85th anniversary of the Holodomor, perhaps the greatest disaster in the history of Ukraine and one of the most terrible tragedies in human history of the last century," the president wrote in a message on Twitter.
Mourning events were expected to take place throughout Ukraine, where the Day of Remembrance for the victims of the famine is marked every year on the fourth Saturday of November.
The Holodomor took place in 1932 and 1933 as Soviet authorities forced peasants in Ukraine to join collective farms by requisitioning their grain and other foodstuffs.
Historians say the seizure of the 1932 crop in Ukraine by Soviet authorities was the main cause of the famine. Moscow has long denied any systematic effort to target Ukrainians, arguing a poor harvest at the time wiped out many in other parts of what was then the Soviet Union.
It is estimated that as many as 9 million people may have died as a result of executions, deportation or starvation during the Stalin-era campaign.
Moscow seized control of Ukraine's Crimean Peninsula in March 2014 and fomented separatism across much of the country — one of the causes of a war that has killed more than 10,000 people in eastern Ukraine since April 2014.
Russia denies it has sent troops, weapons or other support to help the separatists fight government forces in eastern Ukraine, despite what Kyiv and NATO say is incontrovertible evidence.
In a message on Twitter, Poroshenko urged "all political forces to unite for the sake of Ukraine."
He also said that Russia's "aggression against us is a continuation of the same policy to destroy Ukraine with other methods, which Moscow introduced in the '30s of the last century."
Meanwhile, Oleksandr Turchynov, chief of the National Security and Defense Council, said in a statement that "there is a war and we again see manic attempts to destroy Ukraine."
Some material for this report came from AFP.