Nearly 3 million refugees have fled Ukraine since war erupted on Feb. 24. Among them is Hassan Al-Khalaf, an 11-year-old boy from Zaporizhzhia, a southern Ukrainian city along the Dnipro River where Russia has taken control of a nuclear power plant.

Hassan is one of the estimated 1 million children who have made the dangerous journey out of the war-torn country.

"Reports from the border suggest that some children are arriving unaccompanied after being sent by family members who were unable to leave Ukraine but wanted their children to be safe from ground attack and aerial explosions," the charity Save the Children said in a release. "Others have been separated from their families in the chaos of fleeing their homes. Many of the solo arrivals are under 14 and showing signs of psychological distress."

The boy arrived in Slovakia by train and foot, traveling over 620 miles west. The 11-year-old brought with him only a plastic bag with his belongings, including his passport. A phone number was written on his hand.

PHOTO: An 11-year-old boy fled Ukraine by himself, with only a phone number written on his hand. He arrived in Slovakia and was later reunited with his brother in Bratislava.
Slovakia Police
An 11-year-old boy fled Ukraine by himself, with only a phone number written on his hand. He arrived in Slovakia and was later reunited with his brother in Bratislava.

Border guards in Slovakia and volunteers banded together to help Hassan during his harrowing trek, using the phone number to help reunite the boy with his older siblings including his brother, who has been studying in the Slovakian capital of Bratislava.

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At a pro-Ukraine and anti-war rally in the Slovakian capital Friday, Hassan said in an interview, "I got my hope from my mom wanting me to go."

"My hope carried me on my way," he said, according to Reuters.

PHOTO: An 11-year-old boy who fled Ukraine by himself is helped by adults after arriving in Slovakia. He was later reunited with his brother in Bratislava.
Slovakia Police
An 11-year-old boy who fled Ukraine by himself is helped by adults after arriving in Slovakia. He was later reunited with his brother in Bratislava.

Hassan's mother, Pisecka Yulia Volodymyrivna, a widow, made the heartbreaking decision to send her 11-year-old out of Ukraine for his safety and stayed behind to care for her 84-year-old mother, who is unable to walk.

In a video statement, Volodymyrivna thanked the border guards and volunteers in Slovakia, saying in part, "Border guards met him, they guided him holding his hand. They helped him to cross the border and let him to the other side of Slovakia. Then Slovakian volunteers met him. They fed my child. They took him to Bratislava. I thank you very much for saving my son's life."

"I can't leave my mother, who is 84 years old and who can't walk on her own. That is why I put my son on a train to the Slovakia border where he was met by people with big hearts," she continued. "There are people with big hearts in your small country. Please, save our children. Please protect our Ukrainian children."