Chopper 6 was over the scene at JFK Boulevard and N. Broad Street shortly after 8 p.m.
Several of the protesters were waving Palestinian flags while burning other flags - one of which appeared to be an American flag.
At one point, a woman throws several smaller American flags onto the heap.
Chopper 6 video of protest near Philadelphia City Hall
Police say the protest began in Rittenhouse Square and grew to about 400 people.
As the crowd marched down Chestnut Street, police say an act of vandalism occurred and that's when police began to call in more resources.
Officers moved in once the fires started.
"A handful of arrests were made. We're still working out and sorting through that, but that type of behavior absolutely cannot be tolerated," said First Deputy Commissioner John Stanford.
"We are always open to individuals expressing their First Amendment right. We are here for that purpose, of protecting and making sure that everyone has an ability to do so. However, once it turns violent, or there's a situation where individuals are going to destroy property, it changes the dynamic of everything," Stanford continued.
Because of the July 4th holiday, police already had quite a number of officers in the area. They were also aware of the protest, so they had a whole separate group of officers assigned to that.