Flags in colors of the St. George ribbon, a symbol of victory, wave over the crowd as people gather Monday outside the Kremlin in Moscow to mourn victims of clashes in Odessa, Ukraine. (Ivan Sekretarev/AP)

This graceful port city’s residents are famous for their sly sense of humor, not for hatred and ethnic rivalries. So a burst of violence in recent days has many here fearing the worst for the future of Ukraine.

After clashes Friday between pro-Russian and pro-Ukrainian activists resulted in 46 deaths, many residents here say attitudes are hardening fast. Ukraine’s third-largest city has been engulfed by a polarizing battle that until Friday had largely been confined to the country’s east.

On Monday, families buried their dead, the injured recuperated in hospitals and mourners ­arranged flowers at makeshift shrines. Many here are using the word “genocide” to describe the blaze that killed dozens of pro-Russian activists trapped in the House of Trade Unions when someone set the building on fire with a gasoline bomb.

“The first reaction to news about street battles was anger toward the leaders provoking the clashes,” Boris Khodorkovsky, who runs a business communications firm, said Monday. “Everybody throwing molotov cocktails, no matter what political views they have, should be put behind bars so Odessa could live a peaceful life.”

In elegant Ekaterninskaya Square, chestnut trees were in bloom. The spring air was fresh from rain. And two blond women chatted below a statue of Catherine the Great, the empress who founded this city in 1794.

But Khodorkovsky wondered whether the women might one day fill bottles with gasoline and throw them at neighbors who
hold different opinions. Khodor­kovsky’s wife worries about their baby’s safety. His colleagues are talking about leaving town.

And rumors are spreading through this city of 1 million. Someone has poisoned the drinking water, people said Monday. More clashes are coming within days, others said. City authorities, fearing violence, have banned a parade Friday on Victory Day, a holiday of preeminent importance in Russia.

Khodorkovsky said that was a terrible idea, one that might stoke tensions among Russians who feel they are being disrespected. “Nobody in Ukraine has a right to humiliate Soviet history,” he said. “You would be an idiot not to understand the reasons for the conflict.”

A few blocks away, on Kulikovo Square, where the burned-out shell of the House of Trade Unions stands, a man in camouflage was scraping a message to victims on a second-story wall of the building.

“Forgive us, we are all guilty,” Eduard, a 48-year-old engineer, wrote in the soot. He refused to give his last name and said he was wearing camouflage because it was “wartime.”

Whether or not authorities sanction a Victory Day parade, he said, he plans to march.

“We might all die this time, but we will get our revenge on the Banderovtsy for this fire,” he said, using a dismissive term for followers of the Ukrainian nationalist Stepan Bandera. He said he was “dreading” bloodshed in Odessa.

On the square, a few women complained about “anti-Russian guys” raising Ukrainian flags the previous night without waiting for the pro-Russian victims to be buried. “In fear of arrests, victims’ relatives bury their loved ones secretly, as if we live in some fascist state,” said Oleg Driamin, a Cossack volunteer who was guarding the memorials on the square.

But pro-Ukrainians in Odessa say their nerves are frayed, too.

Victor Dementyev, an ethnic Russian who says he is on Kiev’s side, described seeing anti-government activists attack a crowd of young ultranationalist Ukrainian football hooligans Friday. “I know that it doesn’t take much to provoke their fury,’’ Dementyev said of the ultranationalists. “By killing one of their friends, separatists made them crazy.’’

Michael Birnbaum in Moscow contributed to this report.