DONETSK, Ukraine -- Ukrainian forces were reported on Thursday to be mobilizing in the eastern part of the country against pro-Russian separatists in what could be the beginning of long-promised action, apparently centering on the city of Slovyansk, a stronghold of militants allied with the Kremlin.
Elsewhere, the Ukrainian interim authorities said Thursday that “civilian activists” had regained control of City Hall in the southeastern city of Mariupol on the Sea of Azov, forcing pro-Russian protesters to leave without bloodshed.
There was no independent corroboration of the account, published by Arsen Avakov, the interior minister, on Facebook.
News reports offered a different version of the events, saying that the building had been stormed by masked men who used baseball bats to beat the occupiers.
In Slovyansk, separatists rang church bells to sound a general alarm, residents reported.
The intentions of Ukrainian troops were uncertain, however, and it was not clear whether they sought to storm pro-Moscow positions or merely to isolate them.
North of the city, a separatist commander said, Ukrainian and pro-Russian forces clashed at a roadblock in fighting that left one combatant dead and one wounded.
The Interior Ministry in Kiev, the capital, said five people had been killed in fighting around checkpoints.
The events seemed to represent a significant action and a break with an international agreement struck last week in Geneva to defuse tensions.
The clash north of Slovyansk involved Ukrainian troops backed by five light armored vehicles, Reuters reported.
In Mariupol, Mr. Avakov said, the mayoral office was “liberated for normal work” to resume more than a week after pro-Russian protesters first occupied it — part of a string of such moves by allies of the Kremlin, some supported by masked gunmen, in several locations across eastern Ukraine.
While the interim authorities in Kiev have been promising to revive a military effort to reassert control of the eastern part of the country, the campaign had barely registered on Wednesday.
The agreement in Geneva frayed even further as the United States and Russia exchanged warnings and accusations about meddling in the region.
President Obama, on a trip to Asia, warned Russia on Thursday that the United States had more economic sanctions “teed up,” The Associated Press reported, although he acknowledged that his ability to influence President Vladimir V. Putin was limited.
“I understand that additional sanctions may not change Mr. Putin’s calculus,” Mr. Obama said during a joint news conference in Tokyo with Prime Minister Shinzo Abe of Japan, The A.P. reported.
“How well they change his calculus in part depends on not only us applying sanctions, but also the cooperation of other countries.”
In his Facebook posting, Mr. Avakov said there had been “no victims” in the tussle for City Hall in Mariupol, but that bomb disposal experts were checking the building for explosives.
The A.P. quoted Yulia Lasazan, a spokeswoman for Mariupol’s police department, as saying that roughly 30 masked men had used baseball bats to beat pro-Russia protesters after storming the building in the early hours of Thursday.
The occupiers did not offer resistance, even though some of them were believed to be armed, The A.P. said, but called the police instead.
Five people were taken to a hospital, Ms. Lasazan said.
Ms. Lasazan said the police were controlling the perimeter and were negotiating with the remaining protesters, asking them to leave the building.
Source: The New York Times