That figure is higher than any number previously reported. The United Nations was able to verify 2,721 children recruited to fight for all sides in the conflict, the large majority for the Houthis, but officials say that count is likely low, because many families will not speak about the issue out of fear of reprisals from Houthi militiamen.

The Houthis say officially that they don't recruit children and send away those who try to enlist.

Some of the children told the AP they joined the rebels willingly, mainly because of promises of money or the chance to carry a weapon. But others described being forced into the service of the Houthis — abducted from schools or homes or coerced into joining in exchange for a family member's release from detention.

Many can be seen manning checkpoints along main roads across northern and western Yemen, AK-47s dangling from their narrow shoulders. Others are sent to the front lines as foot soldiers.

Children interviewed by the AP said they were targeted by recruiters on soccer fields, farms and, especially, schools.

A 13-year-old named Riyadh said half of the fighters he served with on the front lines in Yemen's mountainous Sirwah district were children. Rebel officers ordered them to push forward during battles, even as coalition jets zoomed overhead, he said.

He said he pleaded with his commander to let the young fighters take cover during airstrikes: "Sir, the planes are bombing."

The reply, he said, was always: "Followers of God, you must attack!"

A 17-year-old boy holds his weapon in Marib, Yemen. Nariman El-Mofty / AP file

An unknown number of child soldiers have been sent home in coffins.

More than 6,000 children have died or been maimed in Yemen since the beginning of the war, UNICEF reported in October. But the U.N. agency has not been able to determine how many of those minors were combatants and the Houthi-run Defense Ministry does not release its records for casualties.

A former teacher from the city of Dhamar said that at least 14 pupils from his school were recruited and then died in battle. Their pictures were placed on empty classroom seats in 2016 during the Week of the Martyr, which the Houthis celebrate each year in February. Most of them were fifth and sixth graders, he said. An education official from Dhamar confirmed his account. The two spoke on condition of anonymity because of fear of retribution.

The teacher said some of the dead children's parents were Houthi leaders who willingly sent their sons to the front lines. "It's painful because this is a child and they are all my children because I was their teacher," he said. "They were taken from the school and returned in coffins."

The Houthis and the coalition forces began peace talks in Sweden two weeks ago, but an end to the war appears far off. Many worry about what will become of the children who fought in the Middle East's poorest country once a peace treaty is signed.

Naguib al-Saadi, a Yemeni human rights activist who founded a Saudi-funded counseling center in Marib for child warriors, said "the real problem with Houthi recruitment of the children will be felt in 10 years — when a generation that has been brainwashed with hatred and enmity toward the West comes of age."

Top Houthi officials heap praise on young soldiers who have died in a conflict they describe as a sacred war against America, Israel and other outside powers they believe are trying to take over the country.

Brig. Gen. Yahia Sarie, a spokesman for the Houthis' armed forces, told the AP "there is no general policy to use the children in the battles," but he acknowledged that some young people do volunteer to join the fight.

"It's personal initiative," the general said. "Some of the children are motivated by the desire to take revenge, thinking it's better to take action and fight with honor instead of getting killed inside our homes." When they try to join, he said, Houthi leaders "send them back home."

He dismissed the accounts from the children who spoke to the AP, saying their claims were coalition propaganda.

But children, parents, educators, social workers and other Yemenis interviewed by the AP described an aggressive campaign that targets children — and is not always completely voluntary. Houthi officials use their access to the Civil Registry Authority and other state records to gather data that allows them to narrow down their target list of the neediest families in villages and displacement camps — the ones most likely to accept offers of cash in return for recruits.

In Sanaa, the Yemeni capital under Houthi control, recruiters go door to door telling parents they must either turn over their sons or pay money for the war effort, according to residents.

Boys recite poems during a session at a rehabilitation center for former child soldiers in Marib, Yemen. Nariman El-Mofty / AP file

The AP interviewed the 18 former child soldiers at displacement camps and a counseling center in the city of Marib, which is controlled by the Saudi-led, U.S.-backed coalition. They had come to Marib after slipping away from rebel forces or being captured by coalition units.

Houthi recruiters assure families their sons won't be assigned to battle zones, but instead will be sent to work behind the lines at roadside checkpoints. Once militiamen get hold of the children, they often instead send them to indoctrination and training camps, and then the front lines, according to two children interviewed by the AP and officials from two child protection groups. The officials spoke on condition of anonymity because of concerns that the Houthis might retaliate by blocking their groups from working in Yemen.