SLOVYANSK, Ukraine — The Ukrainian government on Sunday for the first time sent in its security services to confront armed pro-Russian militants in the country’s east, defying warnings from Russia, Ukrainian officials said.
Commandos engaged in gunfights with men who had set up roadblocks and stormed a Ukrainian police station in Slovyansk, and at least one officer was killed, the officials said. Several officers were injured in the operation, as were four locals, the officials said.
Russian news media and residents in Ukraine disputed that account, saying the Ukrainian forces had only briefly engaged one checkpoint.
In either case, the central government in Kiev has turned to force to try to restore its authority in the east, a course of action that the Russian government has repeatedly warned against.
With tens of thousands of Russian troops massed along Ukraine’s eastern border near Donetsk, Western leaders have worried that Moscow might use unrest in Ukraine’s mainly Russian-speaking areas as a pretext for an invasion, even though the violence had been solely caused by the pro-Russian side.
Both governments intensified their statements Sunday. Ukraine’s interim president, Oleksandr Turchinov, issued another ultimatum, saying separatists should vacate occupied buildings by Monday or face a “large-scale antiterrorist operation” that will include the Ukrainian military.
Turchinov said the Ukrainian Security Council decided to use the army because ‘‘we’re not going to allow Russia to repeat the Crimean scenario in Ukraine’s east.’’ He pledged amnesty to anyone who lays down arms by Monday morning.
Russia claimed that the Ukrainian government was cracking down at the behest of US and European officials.
Speaking on Russian state television, the exiled Ukrainian president, Viktor Yanukovych, claimed that CIA director John Brennan had met with Ukraine’s new leadership and ‘‘in fact sanctioned the use of weapons and provoked bloodshed,’’ the Associated Press reported.
The CIA flatly denied the accusation that Brennan was pulling the strings in Ukraine. CIA spokesman Dean Boyd said that although the agency does not comment on Brennan’s travel itinerary, the ‘‘claim that director Brennan encouraged Ukrainian authorities to conduct tactical operations inside Ukraine is completely false.’’
Yanukovych was ousted in February after months of protests in Kiev, the capital.
The UN Security Council held an emergency meeting Sunday evening at Russia’s request to discuss the crisis.
The police station contested by Ukrainian forces was one of several security centers in the eastern region of Donetsk seized Saturday by masked gunmen in coordinated raids that the Ukrainian authorities denounced as Russian “aggression.”
By Sunday afternoon, the government’s push to reassert its authority in a vitally important industrial and coal-mining region appeared to have made little headway. Pro-Russian protesters appeared to control not only the police station but the entire city of Slovyansk, having set up checkpoints at major streets leading into town.
The protesters blocked a major highway in the east, and flags of Russia and their newly declared and unrecognized People’s Republic of Donetsk flew over administrative buildings in several other midsize towns. These included Mariupol, where protesters seized another building Sunday.
Two rival rallies in another regional capital in eastern Ukraine, Kharkiv, turned violent. At the end of both rallies, a group of pro-Russian protesters followed several pro-Ukrainian activists, beating them with bats and sticks, Interfax Ukraine reported. An attack also was reported on a police station in the nearby city of Kramatorsk.
Roman Svitan, a security adviser to the Ukrainian authorities in Donetsk, said Sunday’s military operation was carried out by Alfa, a special services unit of Ukraine’s State Security Service. He said Ukrainian forces had evicted gunmen from the Slovyansk police headquarters, though protesters there said nothing of the sort had happened.
Svitan said that most of the expelled gunmen were local pro-Russian extremists but that they had also included Russian operatives.
Residents and men standing by barricades in Slovyansk denied that Ukrainian forces had even entered the town Sunday. They said one local man who had been out fishing was in a hospital with a wound from a shooting on a highway outside of town. Russian television said the Ukrainian nationalist group Right Sector had attacked protesters at a checkpoint, injuring the fisherman.
Requests to speak to a leader of the armed men produced a man wearing a ski mask who introduced himself as Alexander and described himself as a deputy commander of the city of Slovyansk after its merger with the People’s Republic of Donetsk. He said Ukrainian armored personnel carriers had opened fire on a barrier of tires on the edge of town.
Ukrainian helicopters buzzed the town, but no soldiers were seen. At one barrier, pro-Russian protesters felled trees across a road into town, guarded by men in ski masks carrying military rifles.
The unrest in Donetsk, capital of eastern Ukraine’s most populous region, began April 6 when pro-Russian activists seized government headquarters and declared the People’s Republic of Donetsk.