TRIPOLI, Lebanon — Over the last two years, Farah Omari has gotten used to phone calls in the middle of the night. Sometimes it is the hospital. Sometimes it is the police. And sometimes it is the street children themselves asking for help.

“We always tell the kids, ‘If anything happens, call us,’” Ms. Omari, 32, said over the sound of a dozen children in the next room. “They can call us 24 hours a day. If anything happens — they get detained, arrested or the child is lost.”

Ms. Omari, who is Lebanese, joined the International Rescue Committee five years ago, first working on a program that protects women. Now she is a senior case manager for the organization’s child protection team, focusing on the northern Lebanese city of Tripoli.

The agency estimates that 1,500 children work on Lebanon’s streets; most are Syrian refugees between 6 and 10 years old. In busy districts, they can be seen on almost every corner, selling gum, tissues, flowers or CDs.