Those are not Pro Mubarak, those are his police force and secret police, which are approx. 1.5 million. He pulled them off the street a few days ago to cause trouble on the streets. Here they are coming back dressed in civilian clothes attacking the crowds as if they are "Pro Mubarak Protesters"
Saudi FM: We hope Iran uses sanction relief for development, not nefarious activities (Reuters)
from the article: Three killed, 600 hurt as violent Cairo clashes run into the night