It's a movie about a creature that feeds on any kind of energy. Not only is it immune to bullets, but they also make it bigger. I think it looks like a cloud and may have tentacles. It sort of infests the areas that it reaches.
I remember people in the streets being pulled by its tentacles when one man finds out his blood is sort of poisonous to it. So he and someone else team up to go to where it all started and kill the creature by pouring lots of blood on its center.
As to the release date, I think it's somewhere between 2000 and 2010, maybe late 90s.