GENEVA (Reuters) - Fuel, cash and medical supplies are running low in parts of Ukraine after Russia's invasion, which could drive up to five million people to flee abroad, U.N. aid agencies said on Friday.

       At least 100,000 people are uprooted in Ukraine after fleeing their homes, while several thousand have already crossed into neighbouring countries including Moldova, Romania and Poland, U.N. refugee agency spokesperson Shabia Mantoo told a U.N. briefing in Geneva.

       "We are still trying to see which civilian infrastructure in Ukraine has been hit where," Afshan Khan, UNICEF’s regional director for Europe and Central Asia, told the briefing.

       U.N. human rights office spokesperson Ravina Shamdasani said that it had reports of at least 127 civilian casualties in Ukraine, including 25 killed and 102 injured, "caused by shelling and air strikes". This was likely a significant under-estimate, she said.

       (Reporting by Stephanie Nebehay)