"Due to the lack of control over their own military on the ground, the occupiers were unable to ensure a proper ceasefire. Also, due to the inherent disorganization and negligence, the occupiers were unable to provide timely transportation of people to the point where dozens of our buses and ambulances were waiting," she said.

Read here In Donetsk direction, Russia is storming Mar'inka and "Azovstal" in Mariupol

The mayor of Mariupol had called on residents of the city to evacuate along a corridor announced earlier in the day by Vereshchuk, announcing three assembly points.

Vereshchuk gave no specifics about how many people assembled, but said, "tomorrow morning we will resume our efforts in the Mariupol direction. I appeal to our people in Mariupol: we will fight for each of you!"

Pavlo Kyrylenko, head of Donetsk region military administration, said in remarks on television Wednesday that fewer people than expected boarded buses along the corridor.

"People gathered at those collection points, but few got on the buses," he said. "Now some of these buses are going on the route determined by the Russian Federation. As soon as they are in touch, we will immediately inform you which of the residents of Mariupol has reached the territory controlled by Ukraine. And we will understand how we will work according to the specified sequence in the next days."