(CNN) As Venezuelans flee their country in search of safety and economic security, another set of dangers awaits them across the border.

In Colombia's northeast, where many Venezuelans have ended up, rival armed groups control illegal border crossings and wreak havoc on civilians with killings, intimidation, sexual violence and recruit children as soldiers, according to a new report by NGO Human Rights Watch.

More than 100 civilians were killed there by the battling groups in 2018, according to the HRW report, which cites United Nations figures. Some Colombian and Venezuelan children have been coerced into either joining groups or enforcing their rules. The report claims that in March, ELN fighters "visited a rural school in Catatumbo to try to convince children to join their ranks." Some children have been threatened for allegedly cooperating with rival groups, according to HRW.

One mother told HRW that local fighters offered her son guns and a motorcycle to work for them, and later warned the family to avoid interacting with government soldiers.

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