UNITED NATIONS - The United Nations on Monday expressed deep shock at the way children are treated in US immigration detention centers, a statement by High Commissioner for Human Rights Michelle Bachelet said.

As a pediatrician, mother and former head of state, Bachelet said, "I am deeply shocked by forcing children to sleep on the ground in overcrowded centers" without access to health care or food, under poor sanitary conditions.

A group of Democratic congressmen and civil rights groups expressed concern over the conditions of the detention centers on the Mexican-American border, which are overcrowded and lack of food, water and other basic needs.

Last week, the inspector general of the Department of Homeland Security published photographs of some detention centers in the Rio Grande Valley, Texas, showing host numbers beyond capacity.

A large number of immigrants from Central America are stranded hundreds of kilometers to reach the United States, hoping for a safe life far from the poverty that is weighing on their country.

US President Donald Trump has been criticized for his tough and illegal immigration stance, especially after the deaths of a number of immigrants held in US centers due to poor conditions.