“Thirty people were evacuated from the rubble, seven of whom were injured. Sixty people were likely to have died under the rubble of buildings,” Gaidai wrote on the Telegram messaging app, adding that two dead bodies had been found.
Reuters could not immediately verify the report.
Ukraine and its Western allies have accused Russian forces of targeting civilians in the war, which Moscow denies.
The Russians were continuing their intensive shelling of the Azovstal steelworks, last bastion of Ukrainian resistance in the ruined southeastern port city of Mariupol, a deputy commander of Ukraine's Azov regiment said on Sunday.
“We will continue to fight as long as we are alive to repel the Russian occupiers,” Captain Sviatoslav Palamar told an online news conference, pleading with the international community to help evacuate wounded soldiers from the plant.
In a week-long operation brokered by the United Nations and the International Committee of the Red Cross (ICRC), scores of civilians who had taken refuge in the plant's underground shelters have been evacuated.
Ukrainian President Volodymyr Zelenskiy said late on Saturday that more than 300 civilians had been rescued and authorities would now focus on trying to evacuate the wounded and medics. Other Ukrainian sources have cited different figures.
Russian-backed separatists said on Sunday a total of 182 civilians evacuated from the plant had arrived at a temporary accommodation point in Bezimenne, in the area they control. Those who wished to go to areas controlled by Ukraine were handed over to UN and ICRC representatives, they said.
In the Ukraine-controlled city of Zaporizhzhia, about 230 km (140 miles) northwest of Mariupol, dozens of people who had fled the port city and nearby occupied areas on their own or with the help of volunteers waited to be registered in a car park, set up to welcome evacuees.
“There are lots of people still in Mariupol, who want to leave but can't,” said history teacher Viktoria Andreyeva, 46, who said she had just reached Zaporizhzhia after leaving her bombed home in Mariupol with her family in mid-April.
“The air feels different here, free,” she said in a tent where volunteers offered food, basic supplies and toys to the new arrivals, many of whom were traveling with small children.