As many as 15 million children find themselves living in conflict-ridden areas in Africa and the Middle East, and even though 2014 has been one of the worst years on recent record for those children, many are forgotten as the attention of the world is elsewhere, the United Nations Children's Fund (UNICEF) said in a statement on Monday.

"This has been a devastating year for millions of children," said Anthony Lake, UNICEF's executive director. "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. Never in recent memory have so many children been subjected to such unspeakable brutality."

The 15 million live mainly in the Central African Republic, Iraq, South Sudan, the State of Palestine, Syria and Ukraine, and comprise a fraction of the globally estimated 230 million children currently living in areas affected by armed conflicts.

UNICEF found that 2.3 million are affected by the conflict in the Central African Republic, and up to 10,000 children have been recruited by armed groups over the past year. More than 430 children have been killed or maimed, which is three times as many as in 2013.

In Gaza, the 50-day conflict during the summer left 54,000 children homeless, and 538 children were killed.

More than 7.3 million children have been affected by the conflict in Syria, with 700 believed to have been maimed, killed or executed this year.

In South Sudan, some 235,000 children under five suffer from severe acute malnutrition, over 600 have been killed and over 200 maimed this year alone.

"The sheer number of crises in 2014 meant that many were quickly forgotten or captured little attention," UNICEF said in the statement. "Protracted crises in countries like Afghanistan, the Democratic Republic of the Congo, Nigeria, Pakistan, Somalia, Sudan and Yemen, continued to claim even more young lives and futures."

The report was released alongside a global appeal by the U.N. Office for the Coordination of Humanitarian Affairs, which called for $16.4 billion to help 57 million people in 22 countries.

"This is not business as usual in the humanitarian world," said António Guterres, the UN's high commissioner for refugees. "Today's needs are at unprecedented levels, and 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."