The appeal is expected to be made on Monday to address urgent basic life needs of the country's displaced population.
"The lack of access to public services previously provided by the central authorities has drastically worsened the plight of the civilian population in areas not under government control. This has been further aggravated by restrictions to the movement of people and goods," UNHCR said in statement.
"Local authorities have begun to evacuate people from conflict areas, but many are still trapped by the fighting, including in basements and buildings under constant bombardment," the statement said.
UNHCR noted Friday that, according to the Ukrainian Ministry of Social Policy, the number of registered internally displaced people in the country stands at 980,000 and is expected to rise.