A mixed-breed rescue dog, shaking loose from her collar during a walk near Second and Arch Streets, attacked a Philadelphia Trolley Works carriage horse leading a tour of Old City shortly after 2 p.m.

According to Melissa Levy, executive director of the Philadelphia Animal Welfare Society (PAWS), six-year old Kelly was spooked upon seeing the much bigger horse strolling beside her, wriggled out of her collar and attacked the horse's from its undercarriage.

Philadelphia Trolley Works declined to comment on the incident. The police report indicated the horse was bitten in the upper left leg area, but was taken back to its stable.

There was no report of any injuries to humans.

During the tussle - which lasted only a matter of seconds, according to Levy - Kelly was briefly caught beneath the cart itself, before a combination of the horse's thrashing and the conductor's attempts to dislodge the dog allowed Kelly to squirm free.

She then took off towards Market Street, Levy said, returning when a PAWS volunteer was able to call her back. Kelly was treated for "superficial paw wounds" and resting, shades drawn, in a room at the PAWS office.

Kelly arrived at the rescue shelter two months ago after her owners threw her from the window of their car.