Commemorations have been held to remember those who died a year ago in the Ukrainian city of Odesa in clashes between supporters and opponents of the government in Kyiv.
In all, 48 people died in Odesa in the May 2, 2014, violence.
Trouble began with fights between two factions marching in the city on the Black Sea.
It ended with a fire at a labor-union building where supporters of autonomy for Ukraine's east took shelter from government backers.
It's unclear how the fire started.
Government supporters did throw firebombs at the building. But official accounts say those inside the building may have caused the fire by throwing firebombs from the roof of the building at their opponents.
Forty-three people died in the building.
In Kyiv, about 1,000 demonstrators gathered for another commemoration, some of them carrying signs saying, "We won't forget, we won't forgive."
Another memorial gathering with flowers and candles took place outside the Ukrainian Embassy in Moscow.
Aleksandr Zakharchenko, leader of the separatist rebels in Ukraine's Donetsk region, on May 2 decried the Odesa deaths as the work of "crowds of brutal Nazis."
"On that day, we and all the citizens of Odesa understood that there is no more country called Ukraine. it is dead for us, together with dozens of tortured Odesa residents," he said.
Konstantin Dolgov, the Russian Foreign Ministry's top human rights envoy, criticized Ukrainian authorities for conducting only "quasi-investigations" into the violence.
The incident deepened divisions in the city where an uneasy calm holds.
On April 1, Ukraine's Security Service (SBU) said it had detained three people suspected of involvement in a series of explosions in Odesa.
The SBU said the three -- who reportedly identified themselves as communist activists -- had confessed to commiting "at least nine acts of terrorism in Odesa" between December and March.
The SBU said a shotgun, chemicals, mobile phone parts, and timers similar to ones used to detonate handmade explosive devices in Odesa were found on the suspects.
A series of bomb blasts have hit Odesa and another eastern Ukrainian city, Kharkiv, in recent months.
Ukrainian authorities blamed those blasts -- many of which seemed to target organizations with ties to soldiers fighting in eastern Ukraine -- on Russia and the rebels who hold parts of the eastern regions of Donetsk and Luhansk.
Both cities, Odesa and Kharkiv, are under the Ukrainian government's control but are seen as prizes coveted by the Russian-backed rebels.