The Ukraine military forced pro-Russia militants to retreat to Donetsk Sunday after the recapture of the town of Slovyansk, signaling a substantial gain for Kiev. 

The Ukraine military said Sunday that they are planning to recapture Donetsk, the eastern capital that rebels proclaimed an autonomous region after a referendum vote, The Wall Street Journal reported. 

Ukraine's military plans to pursue pro-Russia militants who fled to Donetsk from Slovyansk, another "autonomous" region that was the base of the resistance until Ukraine's military forces recaptured the city over the weekend. 

The pro-Russia separatists prepared for a battle in Donetsk as the Ukrainian military gained on them. 

Kiev has now bested the rebels without intervention from Russia. Pressure has been growing from the rebels for Russian President Vladimir Putin to intervene to protect the separatists. 

Fedor Berezin, a rebel deputy defense minister, told The Wall Street Journal that he is disappointed by Moscow's inaction. 

"I'm very disappointed," Berezin said. "That means it will be a long and bloody war until we all die valiantly on the barricades."

The separatists have relied on the Kremlin for military aid after Russia's annexation of Crimea earlier this year. Putin said that Russia annexed Crimea out of concern about Ukraine joining the North Atlantic Treaty Organization and no longer allowing the Russian Black Sea Fleet to have a base in Crimea. 

While Russia has previously provided rebels in Donetsk with weapons, fighters and logistical support, Russia appears to have scaled back helping the rebels. Instead of providing support for the rebels, Moscow is now warning Kiev that its current military operations could alienate a large portion of its Russian-speaking population. 

The Kremlin believes that the rebels will soon be defeated by Ukraine's forces. 

Ukraine Defense Minister Valeriy Heletey told reporters Sunday near Slovyansk that the military offensive against the rebels will continue. The offensive was reignited after the ceasefire declared by Ukraine President Petro Poroshenko ended last week. 

Heletey said the Ukrainian military killed dozens of rebels as they tried to flee Slovyansk Saturday. 

"We will continue the active phase until the moment when on the territory of Donetsk and Luhansk region there is not a single terrorist left," Heletey told The WSJ. 

The fall of Slovyansk could signal the beginning of Ukraine military's victory in recapturing other separatist regions. 

Rebel leaders tried to paint the retreat as a move to strengthen defenses and claimed that they evacuated large numbers of fighters from cities that were recaptured by the Ukrainian military. 

Igor Girkin, a separatist who commanded militants in Slovyansk who goes by the pseudonym of Igor Strelkov, said Donetsk will be easier to defend than Slovyansk. 

"We will try not to make the same mistakes we did in the past. We will be able to prepare for the enemy's next attack more thoroughly," Strelkov told RIA-Novosti. 

Residents in Slovaynsk lived without water or electricity for weeks, and three residents were killed when a barrage hit a five-story apartment building. 

Officials from Kiev said they are trying to re-establish authority in the recaptured cities, and are delivering aid and food to residents. The government transported the supplies to residents Sunday, and electricity was also restored to the city. 

"Everything is being done so that people feel that the war has ended and peaceful life returns," Heletey said. 

President Poroshenko said that more fighting will continue as the military tries to recapture all of the eastern provinces. 

"This is not a complete victory," he said in a televised address after Slovyansk was repcatured. "This is the beginning of a breakthrough in the fight against militants for the territorial integrity of Ukraine."