Police in Philadelphia have released surveillance video of a suspect who allegedly attacked and raped a young woman, then said "Ha ha, I just gave you HIV," before he fled.

The 24-year-old woman was walking home from a friend's house just after midnight on Aug. 29 when she was approached from behind by a man who forced her into an alley, where he physically and sexually assaulted her, police said on the YouTube post.

The man took her purse with her cellphone and ID in it and took off -- but not before he taunted her with the HIV comment, according to the victim's sister speaking to NBC10.

Police told the news channel the "violent, unprovoked" attack may have lasted for hours, and it left the victim with head and facial injuries so severe "to the point of almost being unrecognizable."

She was in hospital for several days and was tested for HIV. The results have not been released.

Philly Mayor Michael Nutter has offered a $10,000 reward for information leading to an arrest and conviction.