UNITED NATIONS, June 19 (Xinhua) -- Children should not be snatched from their migrant parents, Henrietta Fore, executive director of UN Children's Fund (UNICEF), said on Tuesday, in reference to the controversial U.S. practice on the Mexico border.

"Stories of children, some of them just babies, being separated from their parents as they seek safety in the U.S. are heartbreaking," she said in a statement.

"Children -- no matter where they come from or what their migration status -- are children first and foremost. Those who were left with no option but to flee their homes have the right to be protected, access essential services, and be with their families, just like all children."

Detention and family separation are traumatic experiences that can leave children more vulnerable to exploitation and abuse and can create toxic stress, which, as multiple studies have shown, can impact children's long-term development, she warned.

Such practices are in no one's best interests, least of all the children who most suffer their effects. The welfare of children is the most important consideration, she said. "I hope that the best interests of refugee and migrant children will be paramount in the application of U.S. asylum procedures and laws."

Fore noted that the U.S. government and its people for decades had supported UNICEF's efforts to help child refugees, asylum seekers and migrants affected by crises across the globe.

In the past six weeks, more than 2,000 children have been reportedly taken from parents who have crossed illegally into the United States from Mexico. The children have been put in detention centers in southwestern U.S. states.

The newly introduced practice of the Trump administration has drawn international and domestic criticism.

UN Secretary-General Antonio Guterres said Monday that children must not be traumatized by being separated from their parents.

Also, UN High Commissioner for Human Rights Zeid Ra'ad Al Hussein said Monday in Geneva, "The thought that any state would seek to deter parents by inflicting such abuse on children is unconscionable."