2 million people have now fled Ukraine, half children, U.N. says

Just over 2 million Ukrainians have fled their country since Russia began its attack 12 days ago, NPR reports Tuesday per a United Nations tracker.

Of the 2 million refugees, at least half are children, reports UNICEF.  The 2 million total represents about 4 to 4.5 percent of Ukraine's population, notes NPR and Politico.

The number of Ukrainian refugees has "increased exponentially" in recent days, NPR writes; as recently as Wednesday, roughly one week after the invasion began, the total count topped 1 million.

U.N. High Commissioner for Refugees Filippo Grandi confirmed the heartbreaking new figure on Twitter on Tuesday.

 "We've never faced a refugee crisis of this speed and scale," added UNICEF spokesperson James Elder while speaking with CNN early Tuesday morning. "We have almost 1 million children who are refugees ... in under two weeks. This is unprecedented globally, it's harrowing, it's happening as we speak, and it will continue unless we see a cessation of hostilities and this bombing to stop, otherwise we will keep seeing lives ... shattered."

"A dark historical first," Elder later wrote on Twitter, alongside a clip of his CNN appearance.

Overall, the U.N. estimates that as many as 4 million people — or about 10 percent of the population — may flee Ukraine, reports The Washington Post. So far, the vast majority of refugees have fled to Poland, while others have run elsewhere, including Hungary and Slovakia. 

As of Tuesday, almost 100,000 have fled to Russia, the Post notes, per the U.N.