Houthi rebels are using religious centers as venues to recruit children as young as 15 to fight on the front lines of Yemen’s war, a new report from Amnesty International reveals.

Parents of teenage boys lured into combat told the rights organization they learned their sons had been sent to Quranic schools and local centers in Sana’a that encouraged them to join the fight against Saudi forces.

The closure of regular schools due to the conflict, along with growing pressure on Houthi representatives to meet recruitment quotas, have contributed to an increase in child soldiers, Amnesty said it had been told by sources.

Houthis “have been saying that there are so few fighters [at the front line], they are going around taking one [recruit] from each family,” the sibling of a recruited 16-year-old boy told the humanitarian group.

“Many children [are recruited], but people don’t dare to talk or follow up,” said a father. “They’re afraid of being detained.”

Samah Hadid, deputy director at Amnesty’s Beirut regional office, condemned the “shameful and outrageous” violation of international law. “It is appalling that Houthi forces are taking children away from their parents and their homes, stripping them of their childhood to put them in the line of fire where they could die,” she said.

United Nations agencies have documented almost 1,500 boys recruited by warring parties to the front lines of Yemen’s brutal conflict. The U.N. says the actual number of child soldiers could be far greater.

Now approaching its third year, the war has left nearly 19 million Yemenis in need of humanitarian aid, according to a plea for relief assistance from the U.N. A sobering 7 million people in the ailing nation don’t know where their next meal will come from, and now face “a serious risk of famine.”

Yemen, which imports 90 percent of its food, only has food reserves for the next two to four months, the Red Cross reported Tuesday. Some 500,000 people living in the port city of Hodeidah are on the brink of famine as fighting intensifies.