Police are monitoring large groups of roving teenagers in Center City.
Police said they had been alerted that youths planned to gather in the area in response to a dust up earlier in the week at the food court at the Gallery.
The message for the gathering apprently had been spread via the Internet, police said.
Security guards were posted at every entrance to the Gallery Mall on Market Street and reportedly were not letting anyone under the age of 18 in.
Police reported groups of 100 to 200 teens in the areas of Market Street, Sansom Street, Chestnut Street and Broad Street starting around 2 p.m..
One woman who was Christmas shopping reported she had been punched in the face by a girl after she found herself in the midst of 70 to 100 youths on Market Street. The blow bruised her face and knocked out a lens to her sunglasses.
Police have set up a command center at the Gallery.
Six police vehicles responded to a Wendy's on 15th and Chestnut when a call came that there were 100 teens inside. The officers dispersed the group.
In the midst of the confusion, a man robbed a bank at 18th and Market Streets about 2 p.m.