A new United Nations report says the scale of grave violations committed against children caught in conflict intensified in 2015 especially in Afghanistan, Syria, Yemen, Iraq, Somalia and South Sudan.

The annual report on children and armed conflict released Thursday said the U.N. recorded the highest number of child casualties in Afghanistan in 2015 since it began documenting civilian deaths and injuries in 2009.

Secretary-General Ban Ki-moon said in the report that thousands of children are among the more than 250,000 people killed in Syria, and in Yemen the U.N. verified a five-fold increase of children recruited by the warring parties in 2015 compared with 2014.

In Somalia, the U.N. said there was a 50 percent increase in violations against youngsters.