Pro-Russian rebels in eastern Ukraine affirmed on Monday that they were in control of the Donetsk airport, the Associated Press reported.

The city of nearly a million inhabitants serves as the capital of the self-declared Donetsk People's Republic, and the airfield -- though largely destroyed in earlier clashes -- is of significant strategic and symbolic value.

"All attempts of the Ukrainian army to take the airport and to get revenge for the defeat of the last year ... have failed," rebel leader Alexander Zakharchenko said at a press conference early Monday in Donetsk. He said that the attacks launched by forces loyal to Kyiv were of an intensity "never experienced before."

The Ukrainian military used tanks to break through the airport's encirclement and helicopters to evacuate the wounded, the Kyiv Post detailed. The newspaper accused Moscow of sending in reinforcements "each time Russian troops and their proxies in eastern Ukraine face battlefield setbacks."

Officials said three Ukrainian soldiers had been killed and 66 wounded over the past 24 hours, Reuters noted. In terms of the battle lines at the airport, they claimed to have maintained the status quo, though military spokesman Andriy Lysenko said the situation was still very tense.

As the international peace plan for the region continues to crumble, the Kremlin, meanwhile, blasted what it views as a unilateral escalation of the conflict.

"It's the biggest, even strategic mistake of the Ukrainian authorities to bank on a military solution to the crisis," said Russian Deputy Foreign Minister Grigory Karasin, according to state news agency Interfax. "This may lead to irreversible consequences for Ukrainian statehood."

Ukrainian Prime Minister Arseny Yatseniuk, on the other hand, accused Russia of additional cross-border arms deliveries to the separatists, Reuters said.

"Tanks, howitzers, Grad systems, Smerch, Buk," Yatseniuk enumerated at a joint news conference with Polish Prime Minister Ewa Kopacz, referencing Russian-made missile systems which he said were being provided to the separatists.

"Radio-electronic surveillance stations are not on sale in the Donetsk market," Yatseniuk added. "They are only to be had from the Russian defense ministry and Russian military intelligence."