As with most other issues, Moscow and Kiev each blamed the other for the violence.

Vyachislav Ponomaryov, the de facto mayor of Slovyansk appointed by militants, told the Russian newspaper Moskovsky Komsomolets that he had identified the two bodies pulled from the river as pro-Russian militants.

They had died, he said, from stab wounds and been thrown in the river. Mr. Ponomaryov said the city was under attack by a Ukrainian nationalist group, Right Sector, and the Ukrainian Army, although there has been no clear sign of either since a Ukrainian armored column surrendered to the separatists in a humiliating setback for the central government last week.

Ukraine’s Foreign Ministry issued a statement on Sunday dismissing the assertion by pro-Russian militants that attackers in and around the city were members of the Right Sector. The group also denied any involvement.

Over the weekend, armed men in masks robbed the homes of several of the 150 Roma families in Slovyansk, demanding gold and money and telling the Roma that they should leave town. “They pointed a gun at me and said: ‘Where is your gold? Where is your money?’ ” Natasha Cheripovskaya, 45, said in an interview in her ransacked living room.

About a dozen masked men entered the house on Friday, she said, and stayed for about two hours, holding her and a granddaughter at gunpoint. The men, she said, told her that the new authorities in the town had decided that “ ‘we will resettle you outside the town. You aren’t needed here.’ ” The men fired bullets through windows and shot and killed the family’s dog, which was barking, leaving a bloodstain in the yard, she said.