SLOVYANSK, Ukraine — Two days after Ukraine’s interim government declared itself all but helpless to control events in the eastern part of the country, Ukrainian military and police forces resumed their effort to retake this rebel-controlled city on Friday, forcing armed separatists from the city’s outskirts with armored vehicles, helicopters, and ground troops — and seemingly pushing ever closer to a confrontation with Moscow.
The assault began before dawn, and by early morning church bells sounded a general alarm. With helicopters flying along the city’s edge, troops and armored personnel carriers approached the city from multiple sides. The fighting was brief and then sporadic, however, and clashes subsided by early afternoon, before resuming at night.
When movements stopped, the Ukrainian troops had advanced, capturing and holding separatist checkpoints and posting infantry and armored vehicles on a bridge overlooking rail lines by the city’s southern border.
Violence also erupted Friday in the previously calmer port city of Odessa, on the Black Sea, where dozens of people died in a fire related to clashes that broke out between protesters holding a march for Ukrainian unity and pro-Russian activists. The fighting left four dead and 12 wounded, Ukraine’s Interior Ministry said. Ukrainian and Russian media showed images of buildings and debris burning, fire bombs being assembled and men armed with pistols.
The deaths expand the increasingly violent struggle for control over Ukraine’s Black Sea port, which had been quiet until last week, when seven people were wounded in a roadside bombing.
The government’s actions in Slovyansk drew an immediate and indignant protest from the Kremlin, which said Ukraine had effectively destroyed a plan negotiated last month with the United States, Russia, Ukraine, and the European Union intended to deescalate tensions.
Blaming the authorities in Kiev, Ukraine’s capital, a spokesman for President Vladimir Putin of Russia, Dmitry Peskov, told Russian news agencies that “the Kiev regime ordered combat aircraft to fire at civilian towns and villages, launching a punitive operation.”
Moscow repeated its warning that it reserved the right to intervene to protect its interests and Russian-leaning residents of eastern Ukraine. But there were no signs of an imminent move across the border.
In Washington, President Obama and Chancellor Angela Merkel of Germany said Friday that broad new economic sanctions would be imposed on Russia if its threat to eastern Ukraine disrupts the country’s presidential elections, scheduled for May 25.
The warning, delivered during a White House news conference, provided for the first time a specific threshold that Russia must not cross if it is to avoid further sanctions from Europe and the United States.
Those measures could include sanctions against Russia’s lifeblood energy sector, banking system and mining industries, moves that would hurt Europe primarily but also ripple through the US economy.
For weeks, the Obama administration has declined to specify what, short of a Russian invasion of eastern Ukraine, would trigger the most severe sanctions to date in response to Putin’s seizure of Crimea and support for the pro-Russian militias in eastern Ukraine.
Obama and Merkel expressed reluctance to carry out the threat, a reflection of the deep European uncertainty over the costs of doing so.
Russia’s UN ambassador, Vitaly Churkin, speaking in New York, described Ukrainian military operations as “punitive” and said there were English-speaking foreigners among what he called “ultranationalist groups” in Slovyansk.
He accused his Western rivals of double standards, noting that while they had called on Ukraine’s former president, Viktor Yanukovych, to exercise restraint, they condoned the use of force by the current leaders in Kiev.
The US ambassador, Samantha Power, accused Russia of spreading lies and described Ukraine’s reaction to Russian provocation as “reasonable.”
“The Ukrainian people and government have embarked on an effort today to reclaim one city in the eastern part of their country,” she said. “Their response is reasonable, it is proportional, and frankly it is what any one of our countries would have done in the face of this threat.”
The Ukrainian army units in Slovyansk did not seem eager to engage the militants fully and appeared to limit their activities for the day to tightening a cordon around the militant stronghold. The city’s center remained under the control of anti-government militias.
“They are coming at us from all sides,” said one fighter in camouflage and sneakers, who gave his name as Sergei, and who held a Kalashnikov assault rifle and said he was a veteran of the Soviet Army.