"Access remains a major challenge in certain non-government controlled areas, which compromised and impedes the delivery of humanitarian aid," the OCHA's report says.
With no political solution in sight, and the number of internally displaced persons (IDPs) continuing to rise, the situation is dire, the UN office said.
"With more than 1.3 million registered IDPs, Ukraine has now the ninth largest number of internally displaced in the world, according to the Internal Displacement Monitoring Centre," it said.
"Access to water remains a critical issue for many civilians, with up to 500,000 people with poor or no access to water. This increases the risk of water-borne disease outbreaks, especially as temperatures are rising," the report reads.