Women and children account for some 90 percent of those who have fled.
UNICEF, the UN children's agency, said more than 1.5 million children are among those who have fled abroad.
The UN's International Organization for Migration said 186,000 people from third countries had fled Ukraine to neighbouring states. As of Wednesday, some 6.48 million people were estimated to be internally displaced within Ukraine, according to UN and related agencies, following an IOM representative survey.Before Russia invaded, Ukraine had a population of 37 million in the regions under government control, excluding Russia-annexed Crimea and the pro-Russian separatist regions in the east.
Here is a breakdown of neighbouring countries that have welcomed Ukrainian refugees, according to UNHCR:Six in every 10 Ukrainian refugees -- 2,083,854 so far -- have crossed the Polish border, according to UNHCR's latest figures. Many of those heading west from Ukraine into Poland, Hungary and Slovakia then travel further on into other countries in Europe's Schengen open-borders zone.Before the crisis, around 1.5 million Ukrainians lived in EU member Poland, the vast majority of them working.They are mostly those returning to fight but also others seeking to care for elderly relatives or to bring their families out to Poland.