Refugee children fleeing Ukraine arrive in Hungary via humanitarian trains at the Zahony train station this week.-Christopher Furlong/Getty Images

The more than 1.5 million children who have fled conflict-hit Ukraine since Russia invaded last month are at higher risk of falling victim to human trafficking, the group UNICEF warned.

“The war in Ukraine is leading to massive displacement and refugee flows – conditions that could lead to a significant spike in human trafficking and an acute child protection crisis,” Afshan Khan, UNICEF’s regional director for Europe and Central Asia, said. “Displaced children are extremely vulnerable to being separated from their families, exploited and trafficked. They need governments in the region to step up and put measures in place to keep them safe.”

Women and children make up the majority of Ukrainian refugees rushing to other countries, as many men are required to stay behind to fight.

Some of those children are even traveling completely alone. More than 500 unaccompanied children were identified as crossing from Ukraine into Romania from Feb. 24 to March 17, UNICEF said. Unaccompanied children are at an even higher risk of traffickers seeking to exploit the chaos hitting Ukraine, the organization says.

Governments must do more to protect the young and vulnerable, Khan said.

“Children fleeing the war in Ukraine need to be screened for their vulnerability as they cross into a neighbouring country,” said Khan. “Every effort should be made to strengthen screening processes at refugee border crossings.”