Ukrainian President Petro Poroshenko has accused Russia of direct involvement in the sniper fire which killed dozens of protesters incentral Kiev a year ago.
He was speaking as the capital marked the first anniversary of the clashes between protesters and police which toppled ex-President Viktor Yanukovych.
A top Kremlin aide, Vladislav Surkov, had organised snipers, he alleged.
The Russian government hit back at the claim, calling it "nonsense".
More than 100 people died in the violence on Kiev's central Independence Square, known as the Maidan, a year ago.
The anti-Yanukovych revolt was called the "EuroMaidan revolution", as huge crowds demanded a pact with the EU.
In a speech at the Maidan on Friday, President Poroshenko condemned the insurgency by pro-Russian rebels in the east.
Earlier he told Maidan victims' relatives that, according to Ukrainian state security, "the Russian presidential aide Vladislav Surkov led the organisation of groups of foreign snipers on the Maidan".
He was speaking just two days after his army retreated from the key town of Debaltseve, now in rebel hands.