This is in addition to the more than 5.9mn Ukrainians who have left Ukraine entirely since Russian forces invaded on Feb 24.
The figure for the number of internally displaced persons (IDPs) as of May 3, issued by the UN’s International Organization for Migration, is up from the estimate of 7.7mn the IOM gave as of Apr 17.
“The needs of those internally displaced and all affected by the war in Ukraine are growing by the hour,” said IOM director general Antonio Vitorino.
“Access to populations in need of aid remains a challenge amid active hostilities, but our teams are committed to continue delivering urgent assistance inside Ukraine and in neighbouring countries.”
The IOM conducted its latest survey between Apr 29 and May 3.
Sixty-three percent of current IDPs are estimated to be women.
Almost half of the IDPs - more than 3.9mn people - have fled their homes in the eastern region of Ukraine, where Russia is now concentrating its assault.
A further 1.65mn from the Kyiv region have fled their homes, and 1.3mn from the north have been displaced.
The survey found that 36% of IDPs - 2.9mn people - are now in the relatively safer west of Ukraine.
But while a large number of those who fled their homes in east Ukraine are now in the west of the country, a significant number have remained in the eastern region.
Three-quarters of IDPs said they felt somewhat or completely safe in their current location.
The IOM study found that financial support was the overwhelming need among IDPs - chiefly to cover food and medical costs - with shelter another pressing need.
“Nine percent of all people surveyed in the latest report, including those not internally displaced, indicated that their homes were damaged or destroyed,” the IOM said.
“Among the internally displaced alone, this figure rose to 27%. Every one out of 10 people surveyed said that they would need materials to fix damaged homes.”
The survey found that more than 1.2mn people were actively considering leaving their homes due to the war.
It also estimated that 2.72mn people had returned to their homes following at least two weeks of displacement, including former IDPs and people who left the country.
However, “return dynamics remain unsteady and a share of returns reported may not be permanent”, the IOM cautioned.
The survey shed light on the numbers of people currently separated from close family due to the war – 41%, while among IDPs the figure was 64%.
The survey found that 22% of displaced households had children aged one to four, 55% included elderly members and 31% had people with chronic illnesses.
The rapid representative assessment was conducted through interviews with 2,000 anonymous respondents aged over 18 who were contacted at random by telephone.
The survey is used by the IOM to gather insights into internal displacement and mobility and to assess the humanitarian needs in Ukraine.