Mariupol, now mostly Russian-controlled, has been flattened during the 80-day-old war. Ukraine has gradually been evacuating civilians from the devastated city for more than two months.

Refugees first had to get out of Mariupol and then somehow make their way to Berdyansk - some 80km further west along the coast - and other settlements before the 200km drive northwest to Zaporizhzhia.

Nikolai Pavlov, a 74-year-old retiree, said he had lived in a basement for a month after his apartment was destroyed. A relative using "secret detours" managed to get him out of Mariupol to Berdyansk.

"We barely made it, there were lots of elderly people among us ... the trip was devastating. But it was worth it," he said.

An aide to Mariupol's mayor had earlier said the convoy numbered between 500 to 1,000 cars, representing the largest single evacuation from the city since Russia's February 24 invasion.

Iryna Petrenko, 63, said she had stayed initially to take care of her 92-year-old mother, who subsequently died.

"We buried her next to her house, because there was nowhere to bury anyone," she said. For a time Russian authorities had not allowed large numbers of cars to leave, she said.

Only the port city's vast Azovstal steel works is still in the hands of Ukrainian fighters after a prolonged battle.

"My parents' house was hit by an aerial strike, all the windows got blown out," said Yulia Panteleeva, 27, who along with other family members had been absent.

"I can't stop imagining things that might happen to us if we stayed at home," she said.

Australian Associated Press