On Monday, the Ukrainian military accused Russian special forces of participating in attacks against the Ukrainian Donetsk airport, also accusing Russia of smuggling artillery ammunition into the country to prepare for the assault, all despite a ceasefire deal reached in September.
The accusations were confirmed by Ukrainian military spokesman Andriy Lysenko, who told Reuters that intense fighting broke out at the airport "backed by Russian special forces."
"These are Russian special forces. It's already the third day that they've been trying to do something," he told Reuters.
Lysenko said Ukrainian troops caused serious rebel losses and insists that Ukraine has control over both airport terminals.
The increased fighting was linked to a large unauthorized convoy of 106 vehicles reported to have entered eastern Ukrainian territory on Saturday under the guise of providing humanitarian aid. According to Ukraine, the convoy was actually transporting ammunition to separatist rebels.
"The new humanitarian convoy arrived and the terrorists received ammunition for heavy artillery ... therefore they are able to increase the intensity [of attacks]," Lysenko told Reuters..
Because many have been left without food and medical supplies due to months of fighting, Russia regularly sends humanitarian aid shipments of food, building materials and medicine, however the Ukrainian government maintains that such shipments secretly provide military equipment to the rebels.
"The lion's share of humanitarian supplies find their way to the rebels partly in the form of food, but mostly it is ammunition, equipment and other things for combat operations," Lysenko said in a televised briefing, according to Reuters.
Nato Secretary General Jens Stoltenberg said on Monday that there has been "large transfers of Russian advanced weapons, equipment and military personnel to violent separatists."
The Sept. 5 peace deal signed between the two countries has done little to stop the fighting, and shelling has continued from both sides, escalating after elections held by the rebels were deemed to be illegal.