Twenty Palestinian teenagers have been on hunger strike for nine days in an Israeli jail to protest their conditions, a prisoners center said Wednesday. The teens began refusing food last Tuesday in HaSharon jail, Riyad al-Ashqar of the Gaza-based Palestine Center for Prisoners Studies said. They say Israeli prison authorities prevent them from completing their studies, visiting other cells, and accessing adequate food and medical treatment. Some are being held in solitary confinement and banned from having family visits, al-Ashqar added. Israeli authorities regularly raid their cells accompanied by prison dogs, and they are only permitted to use an outdoor yard once a week, in crowded conditions, they said. According to prisoners rights group Addameer, 192 Palestinian children are being held in Israeli jails. At least 39 are under 16-year-old, Addameer says.