The final Ukrainian holdouts, reportedly accompanied by 1,000 civilians, have taken shelter in the city's massive Azovstal steel plant as the deadline of a Russian ultimatum demanding the surrender of Ukrainian forces in Mariupol has passed.
Moscow's ultimatum comes as the local Ukrainian commander warned his troops can hold out for just "days or hours".
But Kyiv says there is a tentative deal to rescue some civilians from the city.
Ukraine's Deputy Prime Minister, Iryna Vereshchuk, wrote on Facebook that women, children and the elderly would be allowed to leave Mariupol under the deal.
The city's mayor, Vadym Boichenko, told national TV that Ukraine hopes to send 90 buses to evacuate about 6,000 people on Wednesday. He said around 100,000 people remain trapped in Mariupol.
Remaining civilians wishing to leave were instructed to gather at 14:00 local time (11:00 GMT), when it was hoped a convoy of buses would take them towards western Ukraine.
But it is not clear whether the evacuation has yet taken place.
"It's too early to tell what will happen," Mariupol Deputy Mayor Serhiy Orlov said.
He added that city officials still hadn't received confirmation from Russian forces that the residents would be allowed out.
The Azovstal Iron and Steel Works - a massive, four sq-mile (10 sq km) plant in the south-east of the city - has become the last centre of the Ukrainian resistance in Mariupol.
