UNITED NATIONS (AP) — Mubin Shaikh told the U.N. Security Council Tuesday that he's haunted by a video image: A 3-year-old boy uses a large knife given to him by his parents to cut off his teddy bear's head.

Shaikh is a Canadian Muslim who was radicalized in his teens, traveled in Taliban-controlled areas and turned away from that "poisonous" way of thinking after the Sept. 11, 2001 terrorist attacks in the United States. He is now an expert on countering violent extremism and said he uses that video — in which the knife is as long as the boy's arm — to train police and intelligence services.

"What will become of this boy when he's 10? 15? Will he even live to 20?," Shaikh asked at a council meeting on children and armed conflict. "This is a real-life story of where we are today and what we will deal with tomorrow."

Shaikh said armed groups deliberately recruit and use children to carry out attacks, build their ranks, and promote their beliefs and agenda.

"Children are easier to forcibly or coercively recruit and indoctrinate" than adults, he said. And "security forces often view children with less suspicion, making them useful as spies, couriers and suicide bombers."

Shaikh said the use of children by such groups is "a growing threat."

He urged coordinated action by governments, the United Nations and civil society to prevent recruitment — and to demobilize and rehabilitate radicalized children.

"One key takeaway for all of you: Youth violence is on a continuum, whether extremism of a religious or racial nature, urban street gangs, banditry, piracy — you are dealing with the same challenge, robbing the innocence of children and leaving them to die," Shaikh told the U.N.'s most powerful body.

Secretary-General Antonio Guterres said last year saw the highest number of child casualties ever recorded by the U.N. in Afghanistan, a doubling of verified cases of recruitment and use of children in Syria and Somalia, and widespread sexual violence against children in Congo, Nigeria, South Sudan and elsewhere.

"Tens of millions of children across the globe were also uprooted from their homes by fighting — their families often split apart, their childhoods disrupted, their futures put at risk," he said.

Guterres called for redoubled efforts and innovative approaches to tackle the problem.

He pointed to measures to better protect children adopted by the security forces in five countries and by four armed groups last year, singling out the release of children from prisons in Somalia and "substantive measures" to reduce child casualties undertaken by the Saudi-led coalition in Yemen.

His annual report on children and armed conflict released in early October put the coalition on a U.N. blacklist for killing and injuring nearly 700 children in 2016.

Last year, the U.S.-backed coalition was put on the blacklist but removed by then-Secretary-General Ban Ki-moon under intense pressure from Saudi Arabia.

For the first time, the U.N. divided the new list into countries that are taking action to curb child casualties — as the Saudi coalition is — and those that aren't.

The U.N. special representative for children and armed conflict, Virginia Gamba, told the council a technical team from her office just returned from the Saudi capital Riyadh "where they reviewed and helped to strengthen" measures the coalition has adopted.

Looking more broadly at the world, she said "children were used as the fuel of war" in 2016 "and they have fared little better in 2017."

"In 2016, over 20,000 violations affecting children were documented," Gamba said. "That is a horrifying number of boys and girls who were subjected to unspeakable acts, mostly by armed groups, but also by government forces, and unknown armed actors."

Guterres said only half of the thousands of children released from armed groups and armed forces last year were successfully reintegrated into their families and communities.

The U.N. chief and the special representative both called for more funding and programs to provide education, job training, counseling and family reunifications for ex-child fighters.