KYIV, April 10 - Ukraine and Russia poured reinforcements into eastern Ukraine this weekend, preparing for what is likely to become the war’s biggest battles as refugees continued to flee the looming Russian assault, The Wall Street Journal reported.

Russia’s main objective now is to seize the parts of the eastern Donbas region not yet controlled by Moscow. Unlike the first phase of the six-week-old conflict, that shift is forcing Ukraine into fighting conventional battles involving tanks, artillery and aircraft on flat, often barren terrain that allows Russia to leverage its superiority in military equipment.

Fresh Russian tank and artillery units, as well as forces withdrawn from areas around Kyiv, began arriving in recent days to staging grounds for the offensive north of the Ukrainian city of Izyum, according to footage shown on Russian military television. Ukraine, too, started moving toward Donbas combat units from areas of northern Ukraine that it recovered after Russian troops retreated.

President Volodymyr Zelensky called for urgent assistance ahead of this new round of the conflict, warning that Moscow hasn’t given up on its aspirations to subjugate Ukraine. “Russia can still afford to live in illusions, gathering new armor and new troops on our soil. And that means that we need even more sanctions, and even more weapons for our state,” he said in a late Saturday video address.

Attempting to disrupt the Ukrainian redeployment, Russia has said that its forces carried out a series of airstrikes on Ukrainian railway hubs. Some 52 people died in Friday’s Russian missile attack on the railway station in the Donbas city of Kramatorsk just as it was packed with civilians trying to board evacuation trains toward the relative safety of western Ukraine, according to Ukrainian authorities. Moscow denied it carried out that particular strike.

Authorities over the weekend urged all civilians in Ukrainian-controlled parts of Donetsk and Luhansk regions—which comprise Donbas—and two districts of the Kharkiv region to use all available means to leave immediately. They organized additional trains and buses.

Russia launched several additional missile strikes on the Dnipropetrovsk region just west of Donbas on Sunday, destroying an infrastructure facility in the city of Dnipro and an industrial facility in the city of Pavlohrad, the regional administration said. Ukrainian forces overnight destroyed a Russian column that was moving toward Izyum, according to the governor of Kharkiv. The claim couldn't be independently verified. (wsj/ez)