An estimated 4 million Ukrainian refugees who fled Russian attacks to neighboring countries may need assistance in the coming months, according to the U.N.

More than 2 million people have already left Ukraine since Russia invaded on Feb. 24, according to data released Tuesday from the U.N. High Commissioner for Refugees (UNHCR).

The U.N. estimates that 12 million people within Ukraine will need relief and protection while 4 million Ukrainian refugees who have left to neighboring countries may need protection and assistance in the coming months, a Ukraine situation update from the UNHCR released Wednesday states.

A man looks up from his cot, at a reception center for displaced persons from Ukraine at the border crossing in Korczowa, Poland, Saturday, March 5, 2022. (Olivier Douliery, Pool Photo via AP)

"At the borders I saw an exodus of people, mostly women and children, along with older refugees and people with disabilities," U.N. High Commissioner for Refugees Filippo Grandi said Wednesday. "They arrived shocked and deeply impacted by the violence and their arduous journeys to safety. Families have been senselessly ripped apart. Tragically, unless the war is stopped, the same will be true for many more."

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More than 1 million Ukrainian refugees who have left the country fled to Poland since March 6.

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"At the borders with Ukraine, I saw an unmatched outpouring of spontaneous solidarity by communities and humanitarians from across each country: local responders were busy, mountains of donations had been built, all effectively organized by border guards, local authorities and communities," Grandi said.

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The agency estimates that an additional million Ukrainians have been displaced internally.

Ukrainians crowd under a destroyed bridge as they try to flee by crossing the Irpin River on the outskirts of Kyiv, Ukraine, Saturday, March 5, 2022. (AP Photo/Emilio Morenatti)

More than 72,000 internally displaced Ukrainians have arrived at 14 locations, mostly in western Ukraine, as of Wednesday. At least 21% of those individuals will continue "moving further," UNHCR said in the situational update.

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Millions of other Ukrainians are living in war-torn areas because they "are stranded, unwilling or unable to leave, due to security risks, destruction of bridges and roads, as well as lack of resources or information on where to find safety and accommodation," the situational update states.

The main issues reported among internally displaced persons in refugee centers include overcrowding, lack of separation by gender or space for family units with privacy, according to the agency, which noted that displaced women and girls face increased risks of gender-based violence.