At least 31 people have died in a fire related to clashes between supporters and opponents of the Ukrainian government in city of Odessa, according to Ukrainian police. The Associated Press notes, the fire broke out in the House of Trade Unions, which had become a makeshift headquarters for pro-Russian separatists in Odessa, but there aren't any details yet on how the fire started.

Earlier reports of 38 dead in the fire were revised later Friday, but Reuters puts the death toll at 40, saying many of those killed died of smoke inhalation or when they jumped from the building to escape the flames. It would be the deadliest day of fighting since President Viktor Yanukovych fled the country in February.

Odessa is a port city, and has a significant population of Russian speakers. But as NBC News notes, it hadn't previously been a major location of tension between supporters and opponents of the new government, until large scale marches broke out today. Earlier on Friday, at least one person was shot and killed in the city, as protesters threw explosive devices and stones at police, according to a law enforcement statement quoted by Reuters. 

The video below was reportedly shot outside the trade union building as it was burning.

Separately, Ukraine's president Oleksandr Turchynov said that a government offensive against protesters in Sloviansk resulted in the deaths of several separatist activists.