The UN Children's Fund on Thursday decried the targeted killing of children by the self-styled "Islamic State" (IS) militant group as a means to punish families trapped in Mosul.

"They are using children as a weapon of war to prevent people from fleeing," said Peter Hawkins, UNICEF's Iraq representative. "This just highlights how indiscriminate and catastrophic this war is."

Read more: US plan to 'annihilate IS' raises questions over civilian toll, larger strategy

IS rose to notoriety in 2014 when it captured large swathes of territory in Syria and Iraq, culminating in the occupation of Mosul, Iraq's second-largest city. In October, Iraqi-led forces launched a major operation to recapture the city.

Backed by a US-led coalition, Iraqi forces have managed to retake most of the city, except for the Old City center, considered the last district under the militant group's control.

What is the 'Islamic State'? Where did it come from? The "Islamic State" (IS) — also known as ISIL, ISIS and Daesh — is an al-Qaida splinter group with a militant Sunni Islamist ideology. It emerged in the aftermath of the US-led invasion of Iraq in 2003 and is led by Abu Bakr al-Baghdadi. Their goal is to create a worldwide "caliphate." It gained worldwide notoriety in 2014 after a blitzkrieg military campaign that resulted in the capture of Mosul.

What is the 'Islamic State'? Where does it operate? IS is believed to be operational in more than a dozen countries across the world. It controls territories in Iraq and Syria. However, the group has lost much of the territory it controlled in Iraq and Syria at the height of its expansion in 2014.

What is the 'Islamic State'? Who is fighting back? The US leads an international coalition of more than 50 countries, including several Arab nations. Russia, Iran and its Lebanese Shiite ally Hezbollah, which all support the Syrian government, also fight IS. Regional forces such as the Kurdish peshmerga (above) and US-backed Syrian Kurdish fighters, fight IS on the ground. The Iraqi army and militia have pushed IS from large parts of the country.

What is the 'Islamic State'? How does it fund itself? One of IS' main sources of income has been oil and gas. At one point, it controlled an estimated one-third of Syria's oil production. However, US-led airstrikes deliberately targeted oil resources and the Syrian government as well as US-backed Syrian Kurdish fighters have retaken most oil wells. Other means of income include taxes, ransom, selling looted antiquities and extortion.

What is the 'Islamic State'? Where does it carry out attacks? IS has claimed responsibility for numerous terrorist attacks across the globe. The militant group has targeted capitals across the EU, including Berlin, Brussels and Paris. IS leaders have encouraged so-called "lone wolf" attacks, whereby individuals who support IS carry out terrorist acts without the direct involvement of the group.

What is the 'Islamic State'? What other tactics does it use? The group uses various tactics to expand its power. IS fighters have looted and destroyed historical artifacts in Syria and Iraq in an attempt at "cultural cleansing." The group has also enslaved thousands of women from religious minority groups, including Yazidis. IS also uses a sophisticated social network to distribute propaganda and recruit sympathizers.

What is the 'Islamic State'? How has it impacted the region? IS has further exacerbated the ongoing Syrian conflict. Millions of Syrians and Iraqis have fled their homes, many traveling to Europe in pursuit of refuge. Although it has lost all of its strongholds, the militant group has left extraordinary destruction in its wake. Areas affected by the militant group's rule will likely take years to rebuild. Author: Rachel Stewart



Millions of children in need of humanitarian aid

Humanitarian organizations have warned that more than 100,000 civilians - roughly half of them children - may be trapped inside the city and purposefully placed in extremely dangerous conditions.

At least 1,075 children have been killed and 1,130 injured since IS captured territory in Iraq in 2014, UNICEF said. It noted that more than 5 million children are in urgent need of humanitarian aid.

Read more: Mosul: The battle for Iraq's future

"Across Iraq, children continue to witness sheer horror and unimaginable violence," UNICEF said in a statement. "They have been killed, injured, abducted and forced to shoot and kill in one of the most brutal wars in recent history."

ls/cmk (Reuters, AP)