Following several days of intense fighting between the Ukrainian military and the pro-Russian insurgency in Donetsk, a top commander of the separatist group said Saturday that the rebels are surrounded in the group's stronghold. 

Igor Girkin, a former Russian officer and separatist leader, said that the main roads that run between Donetsk and Luhansk, "has been taken by the enemy," according to the AP"The Donetsk-Horlivka group of the fighters of Novorossiya is completely surrounded," Girkin said on a rebel social media page, referring to the rebel region in Ukraine. 

The Ukrainian military has not yet confirmed Girkin's claim.

The city, which once had nearly a million residents, has become a ghost town in recent weeks as the population has fled to escape the shelling. As many as 300,000 residents have left the city, making rebel recruiting increasingly difficult, and putting the U.N. on alert for a growing refugee crisis.

"If the Ukrainian army enters our city, this will be the next Stalingrad," one rebel fighter told Mashable. In five-month siege of Stalingrad during World War II, nearly 2 million casualties were suffered between Soviet and Nazi soldiers.