The Ukrainian authorities have blamed pro-Russian foreign paramilitaries for Friday’s violence in Odessa which left at least 46 people dead.
Moscow has pointed the finger at Kyiv and its Western allies.
Saturday morning saw tributes paid outside the burnt-out trades union building where many perished, trapped inside by fire.
Ukraine’s interior ministry says more than 170 people have been arrested – mostly Russian or from Transdniestria, a nearby breakaway pro-Russian region of Moldova where Moscow has a military garrison.
Odessa, calm until now, is far from the unrest in eastern Ukraine – where in Kramatorsk the government claims its forces have retaken key installations in its anti-separatist offensive.
The latest events have brought accusation and counter-accusation.
Kyiv blamed pro-Russian protesters for attacking pro-Ukrainians.
“The provocations that happened in Odessa causing clashes and many victims were the result of outside interference. They were financed by former members of the government of (deposed president Viktor) Yanukovych,” said Kateryna Kosareva,spokeswoman for the Ukrainian Security Service.
A spokesman for the Kremlin blamed Kyiv and what he called its “Western sponsors”.
“The tragedy in Odessa saw nationalists and radicals burn unarmed people alive, with the permission of the authorities. The Kyiv authorities are not only responsible but are also complicit in these crimes,” Russian presidential spokesman Dmitry Peskov told Reuters.
Kyiv says its preliminary investigation into the deadly Odessa fire points the finger at pro-Russian separatists who had barricaded themselves inside.
But reports have suggested that both sides threw petrol bombs.
There is much confusion about the recent events – and fear of still more violence.