[img]http://d.yimg.com/a/p/afp/20100211/capt.photo_1265865260439-1-0.jpg?x=130&y=86&q=85&sig=rOK.fcose0i457Y.etheYg--[/img]AP - Hundreds of thousands of Iranians massed Thursday in central Tehran to mark the anniversary of the revolution that created the country's Islamic republic, while a heavy security force fanned out across the city and moved quickly to snuff out opposition counterprotests.