Russian Foreign Minister Sergei Lavrov says the southeastern parts of Ukraine should be included in talks about the country's future.
He told reporters Tuesday in Moscow that Russia wants to see those regions, which are largely Russian-speaking, represented in multilateral talks.
In Paris, NATO chief Anders Fogh Rasmussen warned that further Russian intervention in Ukraine would be a "historic mistake" that would further isolate Russia from the world.
Also Tuesday, Russia's foreign ministry called on Ukraine to halt what it called military preparations in the southeast that could lead to civil war.
Ukrainian Interior Minister Arsen Avakov said 70 protesters were arrested in an anti-terror operation to drive out pro-Russian demonstrators who seized a government building in the city of Kharkiv.
Pro-Russian demonstrators took over buildings Sunday in the Ukrainian cities of Kharkiv, Donetsk, and Luhansk. They are demanding referendums on splitting with Ukraine -- the same kind of vote that took place last month in Crimea.
The White House says it has evidence that some of the protesters are not local Russian-speakers but were brought in from elsewhere and paid to start trouble.
U.S. Secretary of State John Kerry telephoned Russian Foreign Minister Sergei Lavrov to ask Russia to disavow those Kerry calls separatists and saboteurs.