Russian troops control about 80% of the fiercely contested eastern Ukrainian city of Sieverodonetsk and have destroyed all three bridges leading out of it but Ukrainian authorities are still trying to evacuate the wounded, a regional official said Tuesday. Serhiy Haidai, governor of the eastern Luhansk region, acknowledged that a mass evacuation of civilians from Sieverodonetsk now is “simply not possible” due to the relentless shelling and fighting in the city. Ukrainian forces have been pushed to the industrial outskirts of the city because of “the scorched earth method and heavy artillery the Russians are using,” he said. “There is still an opportunity for the evacuation of the wounded, communication with the Ukrainian military and local residents,” he told The Associated Press by telephone, adding that Russian forces have not yet blocked off the strategic city. About 12,000 people remain in Sievierodonetsk compared to its pre-war population of 100,000. More than 500 civilians are sheltering in the Azot chemical plant, which is being relentlessly pounded by the Russians, according to Haidai. Also Read: Moscow-backed officials try to solidify rule in Ukraine In all, 70 civilians were evacuated from the Luhansk region in the last day, the governor said. A Russian general, meanwhile, says a humanitarian corridor will be opened Wednesday to evacuate civilians from the besieged Azot chemical plant in Sievierodonetsk. Col-Gen. Mikhail Mizintsev said evacuees would be taken to the town of Svatovo, 60 kilometers (35 miles) to the north in territory under the control of Russian and separatist forces. He said the plan was made after Ukraine called for establishing an evacuation corridor leading to Ukrainian-controlled territory. Mizintsev, head of the National Defense Management Center, is accused by Ukraine of human rights violations while commanding troops during the long siege of Mariupol, Ukraine’s key port on the Sea of Azov that has been taken over by the Russians. Russian forces in the last few weeks have pressed hard to capture Ukraine’s eastern industrial Donbas area, which borders Russia and is made up of the regions of Luhansk and Donetsk.  “The situation is difficult,” Ukrainian President Volodymyr Zelenskyy said in a news conference Tuesday with Danish media. “Our task is to fight back.” Jan Egeland, the Secretary-General of the Norwegian Refugee Council, one of the aid organizations supplying food to the people in the Donbas, said fighting in the past few weeks has made regular food distributions impossible. Now, he said, the remaining civilians in the city “are almost entirely cut off from aid supplies after the destruction of the last bridge.”