Women and children make up 80 percent of the 1 million Syrian refugees in Lebanon. They are crammed into cheap apartments, garages and unfinished buildings in towns around the country. The poorest live in informal tent encampments that dot the countryside.

Measures of the extent of sexual exploitation are difficult to come by since women are reluctant to come forward with complaints of abuse for fear of stigma.

But in one sign of their vulnerability and desperation, prostitution has increased significantly in Lebanon, said a police officer in the country’s vice squad. As of July, 255 people, mostly Syrian women, have been arrested this year on prostitution charges, more than the 205 who were arrested during all of 2013, said the officer, who spoke on condition of anonymity in line with police regulations.