The Ukrainian military said on Monday it was preparing for a "final stage" of taking back the city of Donetsk from pro-Russian separatists after making significant gains that have split rebel forces on the ground. Spokesman Andriy Lysenko said Kiev's troops had now cut Donetsk off from the other main rebel-held city of Luhansk, 150 km (90 miles) away, on the border with Russia. "The forces of the anti-terrorist operation are preparing for the final stage of liberating Donetsk," Lysenko told Reuters. "Our forces have completely cut Donetsk off from Luhansk. We are working to liberate both towns but it's better to liberate Donetsk first - it is more important." The city, which had a pre-conflict population of 900,000, rocked to the crash of shells and gunfire over the weekend and heavy guns boomed through the night into Monday from the outskirts of the city.