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The number of people who have fled the war in Ukraine has reached 7,270,939, figures from the UN Refugee Agency show.
More than half have gone to Poland, where 3,817,564 refugees are registered, UNHCR data indicates.
Antonio Vitorino, director general of the UN's International Organisation for Migration, said "the scale of human suffering and forced displacement" was far worse than had initially been expected.
Women and children represent 90 per cent of the refugees, with Ukrainian men aged 18-60 unable to leave due to being eligible for military service.
Romania has taken in 613,435 refugees, while Hungary has accepted 731,098.
The figures show 491,144 people from Ukraine have fled to Moldova, 484,661 to Slovakia and 16,650 to Belarus.
A total of 1,116,387 people fleeing Ukraine have arrived in Russia since the full-scale invasion was launched on February 24.
While the outflow has slowed significantly since March, the UNHCR has projected that 3 million more Ukrainians could become refugees by the end of the year.
“The needs of those internally displaced and all affected by the war in Ukraine are growing by the hour,” Mr Vitorino said.
“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.”
More than 12 million people were displaced in the first eight weeks of the war, Jan Egeland of the Norwegian Refugee Council told reporters.
“People talk about since the Second World War, [but] tell me when in the Second World War there were 12 million people displaced in eight weeks,” Mr Egeland said.
Displacement on that scale took place “over a longer period” back then, he said.
Almost two thirds of Ukrainian children have been displaced from their homes.
The war in Ukraine is a “child rights crisis” where education is under attack, nearly 100 youngsters have been killed in the past month alone and millions more have been forced to flee their homes, the UN children’s agency said.
Before the invasion, Ukraine had a population of 37 million in the regions under government control, excluding Russia-annexed Crimea and the pro-Russian separatist-controlled regions in the east of the country.
European Union and national leaders have been keen to talk of open borders and welcoming refugees. But moving across the continent is not easy, particularly for those who leave with few or no belongings and limited money.
The 27-nation EU has granted Ukrainian refugees the right to stay and work for up to three years, reviving a law that was dormant since the collapse of Yugoslavia in 1992.
If they cannot stay with friends or family, then the bloc has established reception centres to house them. Food and medical care are provided, as are welfare payments and access to schools.
UN's co-ordinated response
The UNHCR has not been limited to documenting the Ukrainian diaspora. It has also co-ordinated a humanitarian response, including attempting to send money to those who have fled.
It began a cash enrolment scheme in Ukraine on March 27.
The UNHCR has said “access to the hardest-hit areas remains extremely challenging, with continuing security risks, both for affected civilians as well as humanitarian actors”.
Ukrainian refugees arrive in Europe — in pictures
