MOSCOW - In a significant boost to Ukraine's efforts to quell a rebellion that has split the nation, government forces on Saturday cleared pro-Russian separatists out of a key rebel stronghold in the east after several days of fierce battles, Ukrainian officials and rebels said.

The recapture of Slovyansk marks a major step for the Kiev government, which has struggled for months to contain a separatist rebel movement that has captured government buildings and cities in the east. Slovyansk had been the site of some of the most intense fighting, and until Saturday, it had appeared to be one of the cities most firmly in rebel hands.

Ukrainian leaders were jubilant Saturday - President Petro Poroshenko ordered the hoisting of the blue-and-yellow Ukrainian flag above Slovyansk's city hall, while Russian officials did not directly respond to rebels' requests for aid. Russian President Vladimir Putin has promised to defend the interests of Russians wherever and whenever they come under attack, but he has left open the question of whether that extends to an outright invasion of eastern Ukraine.

It was unclear whether the capture of Slovyansk marked a decisive turning point in the battle against the separatists, but it appeared to be one of the first times the poorly equipped Ukrainian army has forced the rebels into a major retreat. The fight escalated after a cease-fire expired Monday, with Ukrainian forces using air strikes and artillery bombardment to hit rebel positions. Rebels, meanwhile, have shot down Ukrainian planes.

"This is not a complete victory. But the cleansing of Slovyansk from armed-to-the-teeth gangs of animals has great symbolic importance," Poroshenko said, vowing that the military would soon "liberate" the rest of the rebel-held territories as well, and promising both humanitarian aid and legal amnesty to civilians in recaptured areas.

"This is the beginning of the fight with militants for the territorial integrity of Ukraine," Poroshenko said. He warned, however, that "there are still quite a lot of trials ahead."

Government officials announced they had recovered weapons in Slovyansk left by fleeing militants, including a tank.

"The terrorists are losing, surrendering," Interior Minister Arsen Avakov wrote on Facebook. The Ukrainian military said that two Ukrainian servicemen had died and that 13 were injured.

Some rebel leaders denied the significance of the retreat, saying it was carried out only to protect civilians.

"Ukrainian forces were trying to level Slovyansk to the ground," Andrei Purgin, a top separatist leader, told the Interfax news service. "What would you do if you were being thrashed by mortars, artillery weapons, being bombed from the air - and you had three tanks and machine guns?

"The departure of militias from Slovyansk is a commonplace step to protect civilians from death," Purgin said. "Our resistance is not broken."

Slovyansk was a base for Igor Girkin, a rebel commander and Russian citizen also known by his nom de guerre Igor Strelkov, who posted a YouTube video Friday pleading for Russia to send military aid because separatists in Slovyansk were on the verge of collapse.

On Saturday, high-ranking rebels described the pro-Russian losses as "minimal" and Girkin's withdrawal from Slovyansk as a planned move.

"Kutuzov also departed - and this was the plan," said Pavel Gubarev, the self-proclaimed "People's Governor" of the Donbas region, likening Girkin to the Russian general who defeated Napoleon and suggesting the rebels were simply regrouping. "In general, Russians depart only before a decisive, victorious battle."

Still, Denis Pushilin, the leader of the self-proclaimed Donetsk People's Republic, publicly voiced frustration Saturday, suggesting that the Slovyansk militias had been let down by their Russian patrons.

"What to say. They encouraged us. Encouraged us and abandoned us," Pushilin wrote on Twitter.