The Ukraine authorities say they have seized back control of the regional administration building in the eastern city of Kharkiv from pro-Russia separatists.
They say they hope buildings in Luhansk and Donetsk will be freed shortly as well.
On Monday, pro-Russia demonstrators seized government buildings in the three cities.
Moscow has thousands of troops massed along its border with eastern Ukraine.
Although it insists it has no intention of invading Ukraine, it says it reserves the right to defend ethnic Russians in the country.
Ukraine Deputy Foreign Minister, Danylo Lubkivsky, told the BBC that the situation in eastern Ukraine was “under control but remains dangerous”.
The U.S. had expressed disappointment at the way the Russian government was still destabilising Ukraine.
U.S. Secretary of State, John Kerry, told Russian counterpart Sergei Lavrov in a phone call that “any Russian efforts at invading the country would incur great costs”.
They discussed the possibility of direct talks within the next 10 days.
The U.S. has voiced “great concern” about heightened tension in eastern Ukraine after pro-Russia demonstrators seized government buildings in the three cities.
And so far, the pro-Kiev authorities in Donetsk appear unable to restore order.
Rebels occupying Donetsk’s regional government building declared a “people’s republic” on Monday and called for a referendum on secession from Ukraine to be held by May 11.
Russia recently annexed the Ukrainian peninsula of Crimea, where the majority of people are Russian speakers, following a referendum that Kiev and the West say was illegal.
