KIEV, Ukraine -- In the bloodiest day of violence since Ukraine's former president fled his nation in February, as many as 41 people died Friday in clashes across the country, bringing Ukraine seemingly to the brink of war.
Most of the deaths happened in Odessa, a city hundreds of miles from the primary trouble spots in eastern Ukraine and that until Friday had been mostly devoid of violent protests. Police there said at least 38 people had died, most of them in a fire that raged through a union hall pro-Russian protesters used as a base. Still unknown was whether those who died had been involved in clashes outside the building, and what role, if any, those clashes had in sparking the blaze.
In the east, military confrontations between Ukrainian troops and pro-Russian militias killed at least three people and perhaps as many as seven. Two of the dead were soldiers, killed when their helicopters were blown from the sky by surface-to-air missiles manned by pro-Russian fighters. At least one pro-Russian separatist, and perhaps as many as five, died in fighting in Slovyansk, the city in the embattled Donetsk province that has been the primary flashpoint for the conflict.
The events triggered Russian belligerence at the United Nations in New York, where that country's ambassador, Vitaly Churkin, warned during a meeting of the Security Council that there would be consequences for Ukraine's military moves. "Those who gave the criminal order to unleash bloodshed will bear full responsibility for what happens," he said.
Russia has maintained that it has a responsibility to protect Russian-speaking Ukrainians, who account for at least a quarter of the Ukrainian population nationwide and about half the population in the east. It was the same justification given for moving about 20,000 troops into Crimea in late February and March, leading to what the United States and its allies say was the illegal annexation of the Black Sea peninsula.
There was no sign, however, that Russian troops had crossed into Ukraine. But Ukrainian news reports said would-be Russian saboteurs had been intercepted at the border, and President Barack Obama made it clear in a Washington news conference that U.S. officials remain certain that Russia is stoking the troubles and perhaps arming the militants.
"The notion that this is some spontaneous uprising in eastern Ukraine is belied by all the evidence of well-organized, trained, armed militias with the capacity to shoot down helicopters," Mr. Obama said. "Generally, local protesters don't possess that capacity of surface-to-air missiles or whatever weapons were used to shoot down helicopters, tragically."
At the U.N., Mr. Churkin accused the United States of also stoking the violence. "There was English on the radio waves as well as among those attacking," he said. "English-speaking foreigners were noted in Slovyansk."
But the idea was overwhelmingly rejected at the U.N., where France's representative, Gerard Araud, called Russia "a pyromaniac fireman," and U.S. Ambassador Samantha Power accused Russia of replicating in eastern Ukraine the same "charade" it had employed to annex Crimea. She said Russia's "ridiculous and false" accusations of foreign involvement in the Ukrainian operation suggested that the Kremlin was looking for a pretext to invade with troops posing as peacekeepers.
In Kiev, the interim government's President Oleksandr Turchynov said Ukraine had "started the active phase of anti-terrorist operations" because militants were now "terrorizing the entire Donetsk region." He, too, accused Russia of direct involvement in the fighting in the east. "Our security forces are fighting mercenaries of foreign states, terrorists and criminals who are taking hostages, killing and torturing ... threatening the territorial integrity and stability of Ukraine," he said.
Mr. Turchynov, who'd said earlier this week that "the vast majority of law enforcement officers in the east are incapable of performing their duties," acknowledged Friday that "the operation is not as fast as we would like." Complicating it, he said, was the separatists' "hiding behind civilians, hiding behind hostages and firing on us from multifamily apartment homes." He added: "The criminals suffered heavy losses: many killed, wounded and taken prisoner."
Until Friday, what the Ukrainian government calls its anti-terror operation had been largely ineffective in rousting pro-Russia separatists from the dozens of buildings they have occupied in the country's eastern regions. But Friday, they appeared to have had some success. In Slovyansk, a city of about 125,000 people that is the seat of power for pro-Russia separatists, Ukrainian officials said their forces had overrun at least nine separatist checkpoints and had the town surrounded.
As the Ukrainian military moved in, a separatist leader who is the self-proclaimed mayor of Slovyansk, Vycheslav Ponomariov, released a video in which he asked women and children to stay at home and men with weapons to rise to the defense of the city. "We were attacked. Our city is besieged; there are losses," he said. "We will win."
Ukrainian news reports said the separatists had positioned women and children at the barricades as human shields, stopping national troops from advancing.
The Russian RIA Novosti news service quoted a spokesman for Russian President Vladimir Putin who gave every indication that the Moscow government was preparing to take further steps. "Kiev authorities have launched a punitive operation that destroyed the last hope for the Geneva accords to be effective," the news service said, referring to an April 17 agreement among the United States, the European Union, Russia and Ukraine to take steps to defuse the crisis.
The government move into Slovyansk came the same day that a Russian delegation arrived in the city of Donetsk, allegedly to try to bring about the release of six observers from the Organization for Security and Cooperation in Europe, whom pro-Russia separatists had taken hostage, accusing them of being NATO spies. But the delegation arrived without the knowledge of or an invitation from the Ukrainian Foreign Ministry.
At least 25 other people suspected of being pro-Ukrainian also reportedly are being held hostage in Donetsk. Donetsk separatists also seized a railway control station, cutting electricity to lines and shutting down most rail traffic in the region.
Meanwhile, separatists in Lugansk, in the easternmost tip of Ukraine, agreed to leave buildings they had occupied earlier this week and from which they had raised Russian flags.