MOSCOW — Ukrainian Interior Ministry troops expelled pro-Russian demonstrators from a regional administration building in the eastern city of Kharkiv early on Tuesday, arresting about 70 protesters as the provisional government in Kiev moved to exert control over unrest that the United States and its Western allies fear might lead to a Russian military invasion.
The successful operation to remove the demonstrators was announced by Ukraine’s acting interior minister, Arsen Avakov, who had traveled to Kharkiv to supervise the enforcement effort and described a dramatic overnight siege during which the building was briefly set on fire.
Mr. Avakov, writing on Facebook, boasted that the building had been retaken “without firing a shot, grenades, or other special weapons.” He said the special forces that had carried out the operation in Kharkiv were part of a broader redeployment of Interior Ministry troops to eastern Ukraine aimed at countering the unrest, which the government in Kiev has said is being orchestrated by Russia.
The unrest, in which pro-Russian demonstrators on Sunday evening seized government buildings in Kharkiv, Donetsk, Lugansk and other cities in the region, has posed a delicate challenge for the authorities in Kiev given that Russian armed forces are deployed along the border and that the Kremlin has warned that it is prepared to intervene to protect ethnic Russians in Ukraine.
The Russian Ministry of Foreign Affairs, responding to the deployment of Ukrainian Interior Ministry troops, issued a stern statement accusing the Ukrainian government of embedding within its forces in eastern Ukraine both nationalist militants from the group Right Sector and private American mercenaries from a company called Greystone. It said the American contractors were being disguised as members of a military unit called “Falcon.”
A private American security company affiliated with Greystone, Academi — once known as Blackwater and notorious for its military contracting work in Iraq —, issued a statement in mid-March saying its personnel were not working in Ukraine, after similar allegations surfaced in the Russian press. The company did not immediately respond to the statement from the Russian Ministry of Foreign Affairs.
The ministry, which has repeatedly denounced the government in Kiev as illegitimate and the result of a coup, warned against the use of military force in eastern Ukraine. “We call immediately for the halt of any military preparations, which risk the outbreak of civil war,” it said in its statement.
In Moscow, Foreign Minister Sergey V. Lavrov said on Tuesday that Russia would seek multinational talks on the Ukrainian political crisis that could include the United States, the European Union and “all the political forces in Ukraine,” which should include representatives of the country’s southeast, which includes Donetsk and Lugansk.
“The result, of course, should be constitutional reform,” Mr. Lavrov said at a televised news conference following a bilateral meeting with the foreign minister of Angola.
Mr. Lavrov said the talks should include presidential candidates from the country’s major parties, which would likely include the Party of Regions of the former president, Viktor F. Yanukovych. “We are deeply convinced, and this conviction has not been refuted by anyone so far, it is impossible to calm down the situation and turn it onto the path of national dialogue if Ukrainian authorities continue ignoring interests of the southeast regions of the country,” Mr. Lavrov said.
Mr. Avakov, the acting interior minister, portrayed the expulsion of protesters in Kharkiv as a victory. On Facebook, he wrote: “We, the new team in the Ministry of Internal Affairs, choose to guard the integrity and independence of Ukraine. Glory to Ukraine.”
Hundreds of pro-Russian demonstrators continued to occupy the government administration building in Donetsk, as well as government buildings in other cities.
The seizure of government buildings by pro-Russian protesters has provided a particular public relations challenge for the new Ukrainian government because demonstrators in Kiev who helped oust Mr. Yanukovychhad long occupied government buildings in the capital, including City Hall.
The latest crisis began when several hundred pro-Russian demonstrators in the city of Donetsk declared on Monday that they were forming an independent republic and urged President Vladimir V. Putin to send troops to the region as a peacekeeping force, even though there was no imminent threat to peace.
The actions in Donetsk and two other major cities in eastern Ukraine, which included demands for a referendum on seceding from Ukraine and joining Russia, seemed to be an effort by the activists to mimic some of the events that preceded Russia’s invasion and annexation of Crimea. However, there were no immediate indications that the Kremlin was receptive to the pleas.
While widely regarded as political theater that is supported, if not directed, by the Kremlin, the protests could help promote what analysts say is Russia’s primary goal of destabilizing the shaky government in Kiev, preventing it from drifting further into the West’s orbit and giving Moscow leverage over the country’s future ahead of presidential elections in May.
The turmoil in eastern Ukraine also makes it extremely difficult for the provisional government in Kiev to begin putting in place austerity measures and financial overhauls required by the International Monetary Fund as a condition for an $18 billion loan package that the country desperately needs to avert a default on its debt.
The protesters themselves may be trying to provoke a violent response from Kiev, analysts say, hoping to provide the pretext for a Crimea-like military incursion in a country that Moscow considers an integral part of historical Russia.
In Donetsk, the authorities were able to retake control of the headquarters of the security services, but remained in a standoff with demonstrators occupying the regional administration building. Several thousand people remained on the streets early Tuesday morning, and tensions remained high across the region, with a continuing risk of violence.
In recognition of the potential dangers, Secretary of State John Kerry told Mr. Lavrov, in a phone call on Monday that there would be “further costs” if Russia took additional steps to destabilize Ukraine, the State Department said. Mr. Kerry said in the call that the United States was monitoring with growing concern the pro-Russia protests in Donetsk, Kharkiv, Lugansk and Mariupol, and did not believe they were a “spontaneous set of events,” according to Jen Psaki, the State Department spokeswoman.
“He noted in particular the recent arrests of Russian intelligence operatives working in Ukraine,” Ms. Psaki said.
The Obama administration has warned Russia that it is prepared to impose additional sanctions if Russia intervenes militarily or covertly to undermine the new Ukrainian government, a point Mr. Kerry repeated on Monday.
“He made clear that any further Russian effort to destabilize Ukraine will incur further costs for Russia,” Ms. Psaki said, without providing details. Officials from the United States, Russia, Ukraine and the European Union are planning to meet in the next 10 days to discuss the situation in Ukraine, Ms. Psaki said.
CNATO’s top commander, Gen. Philip M. Breedlove, said last week that the approximately 40,000 Russian troops near the Ukrainian border were capable of intervening in eastern Ukraine on 12 hours’ notice and could accomplish their military objectives in three to five days.
In Kiev on Monday morning, the acting prime minister, Arseniy P. Yatsenyuk, said, “There is a script being written in the Russian Federation, for which there is only one purpose: the dismemberment and destruction of Ukraine and the transformation of Ukraine into the territory of slavery under the dictates of Russia.”
Russian officials, including Mr. Lavrov, have said that they have no intention of taking military action in eastern Ukraine, and in a statement on Monday afternoon, the Russian foreign ministry reiterated its call for federalizing Ukraine, a move that would substantially weaken the government in Kiev, making it vulnerable to manipulation by Moscow.
The unrest in eastern Ukraine seemed to heighten fears in Kiev and the West about possible Russian military action a little more than a month after Russian forces occupied Crimea. The Kremlin annexed Crimea after a referendum there last month.
In Germany, a spokesman for Chancellor Angela Merkel said Monday that the government was extremely concerned about the events in eastern Ukraine and called for calm.
“The latest developments in Donetsk and in Kharkiv are something which we are all very worried about in the German government,” the spokesman, Steffen Seibert, said at a news conference. “We must urgently renew our appeal to all those in positions of responsibility to help stabilize the region and avoid such escalation.”
Even as the Kremlin denied any role, government-controlled television stations in Russia gave live coverage to the events in Donetsk on Monday, including the reading of a sort of declaration of independence of the “sovereign state of the Donetsk People’s Republic” by a pro-Russia demonstrator inside the regional administration building. Protesters occupied the building on Sunday.
While the demonstrators in Donetsk announced that a referendum on secession from Ukraine would be held no later than May 11, there did not appear to be the same overwhelming support for such a move that there was in Crimea last month.
The events in the east unfolded just hours after a Ukrainian military officer was shot and killed in Crimea in a confrontation with Russian troops. A spokesman for the Ukrainian Ministry of Defense, Vladislav Seleznev, said the officer, Maj. Stanislav Karchevskiy, had been killed in a military barracks where he lived with his wife and two children, next to the Novofedorivka air base in western Crimea.
The officer’s death was a rare instance of deadly violence as Ukrainian forces continued their withdrawal from the peninsula after its annexation by Russia. Mr. Seleznev said the Ukrainian had been collecting his belongings in preparation to leave Crimea when an argument broke out with Russian service members, Reuters reported Monday.
Mr. Seleznev said that the altercation had involved several Ukrainian and Russian soldiers and that there had been no other injuries. He said a Russian soldier armed with an automatic weapon had entered the dormitory and shot Major Karchevskiy, who was unarmed.
With tensions intensifying in the east, the former prime minister, Yulia V. Tymoshenko, who is running for president in elections next month, traveled to the region.
At a news conference in Donetsk, Ms. Tymoshenko said she was committed to strengthening the autonomy of Ukraine’s regions, especially by letting them control their finances, but said she opposed federalization. She also said she did not believe most people in Donetsk supported the protesters.
“I got the impression that all of this aggression lives on its own island, separate from the life of Donetsk,” she said. “It does not at all correspond with the opinions or wishes of the people in Donetsk.”