AP PHOTOS: Day 12, humanitarian crisis in Ukraine deepens

The humanitarian crisis in Ukraine is deepening with food, water and medicine growing increasingly scarce as Russian forces intensify their shelling.

In the capital, Kyiv, soldiers and volunteers have built hundreds of checkpoints to protect the city of nearly 4 million, often using sandbags, stacked tires and spiked cables.

“Every house, every street, every checkpoint, we will fight to the death if necessary,” said Mayor Vitali Klitschko.

As Ukrainians attempted to flee Irpin on the outskirts of Kyiv, a Ukrainian police officer could be seen running while holding on to a child as the sound of artillery echoed nearby. The invasion has sent 1.7 million people fleeing Ukraine.

Ukrainian officials accused Moscow of resorting to “medieval siege” tactics in places.

A third round of talks between the two sides Monday ended with a top Ukrainian official saying there had been minor, unspecified progress toward establishing safe corridors that would allow civilians to escape the fighting. Russia’s top negotiator says he expects those corridors to finally start functioning Tuesday.