2014 was one of the worst years on record for children as over 15 million were trapped in conflict-hit countries in Africa and the Middle East, the United Nations Children’s Fund (UNICEF) said, in a statement released Monday. The crisis has been particularly severe in Syria and Iraq, where nearly 10 million children have been affected by the ongoing conflict and forced to witness “increasingly brutal and extreme violence.”

“Children have been killed while studying in the classroom and while sleeping in their beds; they have been orphaned, kidnapped, tortured, recruited, raped and even sold as slaves,” Anthony Lake, executive director of the UNICEF said, in the statement. “Never in recent memory have so many children been subjected to such unspeakable brutality.”

The statement by the U.N. agency, released less than a month after the 25th anniversary of the adoption of the Convention on the Rights of the Child, added that an estimated 230 million children continue to live in countries with ongoing violent conflicts.

However, UNICEF said, the true magnitude of the impact on children had not been fully appreciated as countries around the world were overwhelmed by several near-simultaneous conflicts.

“The sheer number of crises in 2014 meant that many were quickly forgotten or captured little attention,” UNICEF said, in the statement, adding that protracted crises in countries like Afghanistan, Pakistan, Yemen, Sudan, Gaza, Somalia and Congo continue to “claim even more young lives and futures.”

Moreover, in countries like South Sudan, of the 750,000 children displaced by clashes between pro-government and rebel militia, over 230,000 are believed to be suffering from acute malnutrition and are in need of urgent life-saving assistance, UNICEF said, urging world leaders to step up efforts to support children living in some of the “most dangerous places in the world.”

The UNICEF statement was released to coincide with an appeal by the U.N. Office for the Coordination of Humanitarian Affairs (OCHA) calling for a record $16.4 billion in donations to tackle an “unprecedented level of crisis around the world” in 2015.

“Without more support, there simply is no way to respond to the humanitarian situations we’re seeing in region after region and in conflict after conflict,” Antonio Guterres, the U.N. High Commissioner for Refugees said, at a press conference in Geneva on Monday, adding that “business as usual” was not an option anymore.