Two pro-Russian groups were in a standoff against each other in an apparent power struggle in eastern Ukraine on Thursday, igniting rumors that there may have been a small coup within the separatist movement.

As a thunderstorm ominously rolled in through the city of Donetsk, Vostok Battalion, a pro-Russian group that has fought the Ukrainian military alongside other separatists for weeks, surrounded a regional government building that serves as the headquarters for the pro-Russian Donetsk People's Republic. (DPR is what pro-Russian separatists gave call their self-proclaimed state).

Dozens of armed men from the battalion took positions behind trees and around the building's perimeter. The barricades around the building, which DPR constructed when they took it over weeks ago, were torn down, says Mashable photographer Evgeny Feldman, who snapped the images below on Thursday.

But despite how it looks, the Vostok Battalion said this wasn't a coup but rather a "police operation" against looters it claims were in the building. However, some people on the ground are speculating that this move was actually a sign of a power struggle within the pro-Russian separatist movement.

The separatists have been in regroup mode this week after they lost at least 30 fighters in a bloody battle against the Ukrainian military on Monday. Since then, Donetsk has been eerily calm. However, Thursday's standoff could be signs of tiny cracks surfacing within the separatist movement.

Additional reporting by Christopher J. Miller in Donetsk