UNITED NATIONS, Jan. 16 (Xinhua) -- The UN Children's Fund (UNICEF) has highlighted the impact of war on children in Yemen, saying the country has become one of the worst places in the world for children.

Since conflict escalated in March 2015, at least 5,000 children have been killed, said a UNICEF report called "Born Into War -- 1,000 Days of Lost Childhood," which was made available on Tuesday.

An acute watery diarrhea and cholera epidemic have affected over one million people, and children under five account for a quarter of the suspected cases, said the report.

Some 60 percent of Yemeni population are food insecure. Around 1.8 million children under five are acutely malnourished, of whom 400,000 suffer from severe acute malnutrition, a life-threatening condition, it said. Half of all Yemeni children are stunted.

Nearly two million children -- more than a quarter of all school-aged children -- are out of school during the 2016-17 school year, including half a million who dropped out since the conflict escalated in March 2015. Some 4.5 million, or 78 percent of all students, are at the risk of missing one year of school, it said.

More than half of children have no access to safe drinking water or adequate sanitation. Nearly every single child -- 11.3 million in total -- needs humanitarian assistance, said the report.

Yemen has been in civil war since 2012.