The air traffic control tower at Donetsk Airport has been destroyed by pro-Russian forces surging from two sides against a depleted Ukrainian military. Separatist forces had offered a 5 p.m., local time, deadline (10 a.m. EST) for the government's soldiers to vacate the airport, but Ukrainian artillery reinforcements have slowed the attack, according to the Ukrainian Independent Information Agency.

The Donetsk airport has been the focal point of continued fighting in Ukraine despite a ceasefire signed in September. A meeting between France, Germany, Russia and Ukraine was due to take place in Astana, Kazakhstan, on Thursday, but in the early hours of Tuesday morning all sides called off the meeting, citing a lack of progress.

According to Liga, a Ukrainian news website, separatist forces were within 400 meters when the control tower fell. However, it’s yet to be seen whether additional artillery support will be enough to keep the airport from falling into pro-Russian hands -- a development that would give an important tactical advantage to the separatist forces battling the Ukrainian government's troops.

“If we do not leave, the terrorists [pro-Russian separatists] will simply destroy us," a soldier told Liga. "The shelling is sweeping through the terminal. But we’re not going anywhere.”

The destruction of the tower, which had been a symbol of Ukrainian resistance at the airport, was confirmed to Hromadske.TV by a Ukrainian commander of the Right Sector volunteer corps. The Ukrainian Independent Information Agency said that fighting had raged for three days before the tower fell.

On Monday night, pro-Russian forces fired rockets at the airport followed by tank fire and heavy artillery in the morning. While Ukrainian commanders have complained that they are unable to evacuate their wounded from the airport, Ukrainian artillery fire at separatist targets has offered some respite for soldiers inside the airport.

In the meantime, peace talks remain stalled. “The differences in opinion made it clear how difficult it is to make progress towards a political solution or a summit in Astana, from which much is expected and which must be prepared," German Foreign Minister Frank-Walter Steinmeier said.