DONETSK, Ukraine — Ukrainian government troops on Wednesday claimed to have swept out pro-Russia gunmen from a town in embattled eastern Ukraine, an operation the Kremlin warned could spark retaliation.
The Ukrainian Interior Ministry statement that Svyatogorsk was under government control was dismissed as "a propaganda lie" by a leader of insurgents holding nearby Slovyansk, scene of the most violent and destabilizing clashes of the separatist movement that has been gaining momentum since Russia's annexation of Crimea last month.
Vyacheslav Ponomaryov, the gunman who has proclaimed himself mayor of Slovyansk, confirmed that his armed group was holding 10 hostages, including an American journalist, and demanding the release of Russian agents and fighters detained by Ukrainian forces trying to reassert Kiev's authority in the turbulent east.
"These Ukrainian guys and this American are not really journalists but provocateurs, and they will stay here until we exchange them for our comrades put in prison by the illegal government in Kiev," Ponomaryov said in a telephone interview. "I am warning that if we are attacked none of [the hostages] survives."
Ponomaryov expressed willingness to exchange Simon Ostrovsky, a reporter for Vice News who was abducted Monday by the Russian gunmen, for Pavel Gubarev, the jailed leader of the separatist forces in the neighboring Donetsk region. Ostrovsky holds both U.S. and Israeli passports.
Armed factions agitating for independence from the Kiev government, and in some cases for annexation to Russia, have taken over key government facilities in a dozen towns and cities across eastern and southern Ukraine.
The Kiev leadership launched its operation to retake control from the insurgents last week but managed to liberate only one small airfield. The armored columns dispatched by Kiev were attacked at some of the roadblocks erected by the militants, who seized six armored vehicles. As many as 300 of the poorly equipped Ukrainians were reported to have defected to the separatist side.
Ukraine suspended the mission last week to recover its seized sites after top diplomats from Russia, the United States, the European Union and Ukraine agreed on steps to "de-escalate" the confrontations. Kiev leaders said the pause was to allow Easter celebrations and time for the militants to contemplate an amnesty offered in exchange for disarmament and release of facilities under rebel control.
None of the occupations has ended, however. The recovery operation resumed Wednesday after the bodies of two government supporters from Slovyansk, including a city councilman, were found in a river, each bearing signs of torture.
In Moscow, Russian Foreign Minister Sergei Lavrov accused the United States of orchestrating the Ukraine crisis for geopolitical gain. He drew a link between the Tuesday visit of Vice President Joe Biden and the interim government's decision to resume efforts to restore Kiev's authority in the seized regions. Lavrov called the sweep "criminal" and warned that it could force Russia to defend its interests. He drew an ominous parallel with Russia's 2008 war with Georgia over its breakaway South Ossetia region.
"Russian citizens being attacked is an attack against the Russian Federation," Lavrov said in an interview with state-run Russia Today television. "If we are attacked, we would certainly respond. If our interests, our legitimate interests, the interests of Russians, have been attacked directly … like they were in South Ossetia for example, I do not see any other way but to respond in accordance with international law."
Russian troops fought a brief war against the former Soviet republic of Georgia in support of pro-Russia rebels who had seized South Ossetia in a fashion similar to events in Ukraine.
"There is no reason not to believe that the Americans are running the show," Lavrov said of the unrest that has beset Ukraine since November, when protesters took to the streets of Kiev and other major cities in anger at former President Viktor Yanukovich's decision to abandon an economic association pact with the European Union. His ouster in late February spurred Russia to infiltrate and seize Ukraine's Crimean peninsula, which it annexed last month after a vote condemned as illegitimate by most U.N. member states.
Russian officials insist that the militants in eastern Ukraine are locals opposed to the opposition politicians who took power after Yanukovich fled in February. U.S., European and Ukrainian leaders accuse Moscow of having instigated uprisings by ethnic Russians, and sending Russian troops to support and direct them.
The recapture of Svyatogorsk, as claimed by the Ukrainian government, could signal that Kiev is gaining momentum in its efforts to counter the territorial seizures, said Dmitry Tymchuk, head of Kiev's Center for Military and Political Research. "It appears that our law enforcement units in the Donetsk region have finally got their act together."
Loiko reported from Donetsk and Williams from Los Angeles. Special correspondent Victoria Butenko, in Kiev, contributed to this report.