Demonstrators have gathered in the Ukrainian city of Odessa to mark the second anniversary of the street clashes that culminated in a fire that killed 43 people as they took shelter from opponents.

In all, 48 people died in the May 2, 2014, violence. It began with fights between two factions marching in the city, one supporting the recent overthrow of the pro-Russia president and the other calling for autonomy for Ukraine's heavily Russian east.

The autonomy supporters eventually took shelter in a trade union building. Their opponents threw firebombs at the building, which caught fire. However, official accounts say those who took shelter in the building could have set it on fire by throwing firebombs from the roof.

Monday's demonstrators were blocked from the immediate area outside the building.