Palestinians tossed a pipe bomb into a Hebron school that Israeli soldiers had seized, and troops fired volleys of rubber bullets at the rioters, targeting even those evacuating the wounded. Twenty Palestinians were injured by rubber bullets during several hours of street clashes. Two soldiers were injured by rocks. Clashes have erupted daily in Hebron since last week, after a Jewish extremist hung posters depicting the prophet Muhammad as a pig. The latest clashes began when Palestinian youths arrived with buckets of stones and began hurling them at troops. At one point, the rioters threw a pipe bomb into the courtyard of an elementary school the soldiers were using as a lookout. The blast shattered windows, but the startled soldiers escaped injury.