• A Palestinian boy cries as he stands near his house destroyed by Israeli airstrikes.Reuters
  • A soldier escorts schoolchildren after they were rescued from from the Army Public School that is under attack by Taliban gunmen in Peshawar, December 16, 2014.Reuters
  • Shoes lie in blood on the auditorium floor at the Army Public School in Peshawar.Reuters
  • A child from the minority Yazidi sect, fleeing the violence in the Iraqi town of Sinjar, rests at the Iraqi-Syrian border crossing in Fishkhabour, Dohuk province.Reuters
  • A newly released chilling video shows ISIS jihadists negotiating price for Yazidi sex slave girls as young as 15.YouTube/ Screenshot
  • One of the over 200 Chibok girls was found abandoned in Mubi.YouTube Screenshot
  • nullnull

"This has been a devastating year for children," the United Nations Children's Fund (UNICEF) declared, as the world witnessed one of the worst conflict-ridden years that affected millions of children.

From the Gaza war that killed hundreds of children, and the families and children displaced in conflict zones in the Middle East, to the Boko Haram kidnapping of Chibok schoolgirls, and the most recent incident of the Peshawar school attack on 16 December that left 132 school students dead, children have borne a heavy brunt of conflict and terrorism.

"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," UNICEF Executive Director Anthony Lake said in a new report released earlier this month, even before the Peshawar carnage.

According to the report, up to 15 million children were caught up in conflicts in the restive regions of Iraq, Syria, South Sudan, the State of Palestine, Central African Republic, and Ukraine.

More children are likely to fall victims of increasing conflict, as UNICEF highlighted that as many as 230 million children are currently living in countries affected by conflict.

Some of the most disturbing incidents that affected children this year are as follows:

Peshawar School Attack: The most recent incident of the Peshawar school attack on 16 December that left 132 school students dead was one of the deadliest such attacks on children anywhere in the world, perpetrated by the Taliban's Pakistan faction.

The school attack sent shockwaves across the world over the cold-blooded brutality of the terrorists, who targeted students in an army school to seek revenge against the Pakistan military's offensive on militants.

Terrorists stormed into classrooms and shot dead students after lining them up, reports suggested, and stories of horror poured in in the following days as survivors gave chilling accounts.

'Death was Approaching me': Boy Plays Dead to Survive Peshawar Attack; Describes Militants Pumping Bullets into Children

Pakistan Terror Attack: Peshawar School Siege Over; 132 Children Dead

Peshawar School Attack: Lucky Boy's Life Saved by Faulty Alarm Clock

Peshawar School Attack: Inside Images of Brutal Mishap Released; Nawaz Sharif Visits Survivors [PHOTOS]

Gaza War: Earlier this year, the 50-day Gaza conflict, said to be the deadliest assault by Israel, had killed more than 2,000 Palestinians, of which 538 were children, according to UNICEF.

54,000 children were left homeless, and 3,370 were injured as bombs pounded the Gaza strip.

One of the most heart-wrenching incidents from the war was when four children playing on the beach were killed by an Israeli air strike.

Four cousins, all under 15, were playing football on the beach in Gaza when two missiles struck this July, killing them all instantly.

The conflict itself was said to have been triggered by the gruesome murders of Israeli and Palestinian teenagers.

Gaza: 4 Innocent Children were Bombed while Playing Football

Israel-Hamas Ceasefire Too Little, Too Late; Truce Changes Little for Gaza after 2,000 Lives Lost

Netanyahu 'Justifies' Gaza Civilian Deaths; Israel Offers to Extend Ceasefire

Islamic State Takes Yazidi Girls as Sex Slaves: The rise of the brutal Islamic State, previously known as ISIS, in Syria and Iraq had a deadly impact on the children in the region, especially on the minority communities of Yazidis and Christians, which were persecuted by the terror group.

Even while thousands of Yazidis fled their homes and took refuge on Mount Sinjar for months, several were kidnapped by ISIS militants, who took young girls as sex slaves.

Some shocking reports revealed that Yazidi and Christian girls as young as one to nine years of age were being sold for a price of $172 in Iraq.

Traumatic accounts of some of the girls raped by the militants

There were also disturbing reports of Islamic State beheading children or forcing them to watch gruesome killings.

At least 700 children are believed to have been maimed, killed or even executed this year in Iraq, according to UNICEF.

ISIS Releases Chilling Checklist of How to Treat Thousands of Kidnapped 'Yazidi' Sex Slaves

ISIS Beheads Four Children for Refusing 'to Convert to Islam and Betray Jesus'

Shocking: ISIS Official 'Slave' Price List Shows Yazidi, Christian Girls Aged '1 to 9' Being Sold for $172

Syrian Conflict: In Syria, more than 7.3 million children were affected by the conflict between the Syrian regime and anti-government forces, including 1.7 million child refugees, according to UNICEF.

The United Nations said there were about 35 attacks on schools in the country this year, which killed 105 children and injured nearly 300 others.

Mass Grave of 230 from a Syrian Tribe Killed by ISIS Found [VIDEO]

Timelime and Facts on ISIS: Its Phenomenal Rise that made 2014 the Bloodiest Year of All

Raqqa: ISIS Beheads Muslim Man for Blasphemy as Child Fighters Look on [PHOTOS]

Boko Haram Kidnappings: The Boko Haram militants in Nigeria, who are against Western education, kidnapped more than 200 schoolgirls from Chibok this April, whom they threatened to sell as sex slaves.

Reports emerged that many of the young girls had been converted to Islam and married off to militants, while some reports claimed the girls were also being used as suicide bombers.

The kidnapping led to the global #BringBackOurGirls campaign, which saw prominent political figures and film celebrities take up the cause to free the girls.

The Boko Haram militants also kidnapped 100 boys from a village in Borno State in Nigeria this year.

Arrested Boko Haram Leader Claims he Married Two Abducted Schoolgirls

Four Months Pregnant Chibok Girl Abandoned by Boko Haram

Boko Haram Kidnaps more than 100 Women and Children in Nigeria Village, Kills Scores

Boko Haram Kidnaps 100 Boys from Borno Village

Conflict in Africa: 2.3 million children in the Central African Republic have been affected by the conflict, and a staggering 10,000 children are believed to have been recruited by armed groups over the last year, UNICEF said.

The number of children killed or maimed in the region has tripled since 2013, with more than 430 such incidents recorded.

The statistics are even more disturbing in South Sudan, where 600 children have been killed and over 200 maimed this year, and around 12,000 children are now being used by armed forces and groups.

If not conflict, the Ebola epidemic wreaked havoc in Western African countries this year, leaving thousands of children orphaned and an estimated 5 million out of school.

Sudan: Tribal Gunmen Riding Horses and Camels Kill 15 in south Darfur

Sudanese Woman, Sentenced to Death for Embracing Christianity, Gives Birth in Jail

Sewol Ferry Tragedy: While the Sewol ferry tragedy was not a conflict-related incident, the capsizing of a ferry on 16 April that killed 300 school children off South Korea's coast saddened the world, and reports of mismanagement by the crew led to widespread anger.

Several crew members, including the captain, abandoned the sinking ship, leaving hundreds of children trapped on board.

South Korean Sewol Verdict: Captain of Capsized Ferry Gets 36 Years in Prison

6,000 South Korean Police Raid Church in Search of Sunken Ferry's Owner Yoo Byung-un

As the year ends on a grim note for children around the world, it puts in perspective the effort required to make 2015 a better year for them.

"The world can and must do more to make 2015 a much better year for every child. For every child who grows up strong, safe, healthy and educated is a child who can go on to contribute to her own, her family's, her community's, her nation's and, indeed, to our common future," UNICEF said.