The police chief in Odessa is calling on residents of the Ukrainian port city to remain calm in the wake of violence between government supporters and opponents that left at least 42 people dead.

The deaths came Friday in a clash that started with street fighting then turned into a conflagration when government opponents took shelter in a building that then caught on fire, reportedly because of firebombs thrown through the windows.

The local office of the emergencies ministry said Saturday that 36 bodies were discovered inside the building. Before the fire, police said at least three people were killed by gunfire. The Interior Ministry on Saturday said the total casualty toll was 42, but did not give a breakdown.