An AFP report translates:
Access to the Facebook site was prohibited several days ahead of the presidential election," Ilna [Iranian Labour News Agency], considered close to Iranian reformists, said in reference to the June 12 vote.
"According to certain Internet surfers, the site was banned because supporters of Mir Hossein Mousavi were using Facebook to better disseminate the candidate's positions."
An employee of an Internet service provider who requested anonymity said the ministry of communications and information technology had announced the decision.
However, there was no immediate comment from the authorities on the claims. Former prime minister Mousavi is backed by two-time ex-reformist president Mohammad Khatami and the main reformist parties. He is considered to be the main rival to hardline incumbent President Mahmoud Ahmadinejad, who is seeking a second four-year term.
The story is almost certainly true: the BBC reports that CNN employees in Tehran cannot visit Facebook: their ISPs deliver the message "Access to this site is not possible."
The block, meanwhile, makes a total mockery of Iran's supposed "elections": Iranian television and radio are already state-controlled, and putting a lockdown on websites like Facebook further limits the potential for open discussion of the candidates.
Ahmadinejad's opponent, Mir Hossein Mousavi, currently has over 4,500 Facebook fans on one fan page, and multiple fan pages are said to exist. Facebook has responded to the incident, calling it "a shame". "An outrage" might be the more appropriate word choice.