(NewsNation) — After a Sunday cease-fire collapsed, Russian officials announced another attempt for Monday. This agreement provides a window for people to flee the capital city of Kyiv along with Kharkiv, Mariupol and Sumy.

A third round of talks are also planned for Monday, but the rhetoric from each nation is heated as the fighting enters day 12. Both sides blamed each other for the failure of previous cease-fire agreements.

Ukrainian officials said Russian artillery fire and airstrikes prevented residents from evacuating the eastern city of Volnovakha and the southeast port city of Mariupol. Putin accused Ukraine of sabotaging the effort.

In Mariupol, a city of about 430,000, shelling from Russian forces intensified. Mariupol Mayor Vadym Boychenko told Ukrainian TV that thousands of children, women and the elderly came under fire as they prepared for a possible evacuation.

“The city is in a very, very difficult state of siege,” he said. “Relentless shelling of residential blocks is ongoing, airplanes have been dropping bombs on residential areas.”

Reports say cities under siege are running low on food, water and medicine. Meanwhile, volunteers in western Ukraine are working to package food supplies for besieged areas such as Mariupol.

“It’s difficult to see all those things, and struggling, and violence — but I am also inspired by the spirit of people. and the people are united,” said a volunteer.

The number of refugees continued to rise Sunday, even though the humanitarian corridors meant to ease the passage of civilians collapsed as quickly as they were agreed upon.

Filippo Grandi, the United Nations high commissioner for refugees, said the humanitarian corridors were not only critical to evacuating vulnerable civilians but to getting basic goods in to those still trapped by the conflict.

“But what is needed really is a cease-fire, the end of hostilities, because that’s the only way to stop this tragedy,’’ Grandi said.

The sentiments were echoed by Pope Francis, who made a powerful appeal for peace at the Vatican on Sunday, imploring “an end to the armed attacks, and that negotiations prevail.”

In a highly unusual move, the pontiff said he had dispatched two cardinals to the war-ravaged country, signaling that the “Holy See is ready to do everything in the service of this peace.”

“In Ukraine, rivers of blood and tears are flowing,” the pope said during his traditional Sunday blessing. “This is not just a military operation, but a war that is spreading a lot of destruction and misery. The victims continue to become more numerous, just like the people who are fleeing.”

As of Sunday, more than 2,000 civilians have died since the start of the invasion, according to the Ukraine State Emergency Service.

Ukrainian President Volodymyr Zelenskyy continues to call world leaders for aid as Russia continues to attack.

“I’ve just heard the report on the missile strike in Vinnytsia. Eight missiles against our city, against our peaceful Vinnytsia, which has never posed a threat to Russia in any way.” Zelensky said in a video posted on Twitter. “A brutal, cynical missile strike has completely destroyed the airport.”