A pro-Russian militant wearing a surgical mask guards a barbed wire covered barricade in front of the Donetsk regional administration building on April 8, 2014.
Is Russia instigating Ukraine protests?
01:44 - Source: CNN

Story highlights

NEW: Kerry and Lavrov discuss the situation in eastern Ukraine in two phone conversations

U.S. ambassador tweets pictures he says show Russian buildup

"We are always vigilant," Defense Secretary Chuck Hagel says of Russia's moves

Ukraine's acting interior minister says unrest in eastern region will be resolved in 48 hours

Kiev CNN  — 

Ukrainian acting Interior Minister Arsen Avakov said Wednesday that the separatist protests in Ukraine’s eastern region would be resolved within 48 hours – either through negotiations or the use of force.

At the same time, Russia insisted that the presence of its troops just over the border was no reason to worry.

The United States and others have accused Russia of fomenting the separatist unrest as a pretext for military intervention.

Using classified and commercial satellite imagery, the United States estimates there are up to 40,000 Russian troops on the border with eastern Ukraine. NATO has also warned of a major troop buildup.

The U.S. ambassador in Kiev, Geoffrey Pyatt, posted photos via Twitter on Wednesday to illustrate the U.S. estimates.

The photos depict what is supposedly a field outside the Russian city of Rostov – empty in October, filled with troops and armored vehicles on April 2.

A U.S. official with direct knowledge of the matter told CNN those photos “are consistent” with classified imagery.

Washington is sharing some information with the Ukrainians, but not highly classified intelligence, the official said. Ukraine was aligned with Moscow until a month ago, and it is believed Ukraine’s security services are still penetrated by the Russians, the official said.

But Russia’s Foreign Ministry said Wednesday that Ukraine and the United States have “no reason for concern” about the presence of Russian forces, which it says are on military exercises.