Social networking site Facebook has been blocked in Iran since Saturday, according to the country's opposition, as opposition voters increasingly turn to online tools like social networking to promote their candidates.
Iran will hold elections in June for a new president.
Lacking other suitable media, youth in Iran were using Facebook to promote opposition candidates, and to convince people to participate in the elections, Mohammad Ali Abtahi, a former vice president of Iran and a reformist politician, said in a post on his blog.
Abtahi blamed supporters of current president Mahmoud Ahmadinejad for blocking Facebook.
Facebook, blogs and similar websites are a key component of the election strategy of reformist candidate Mir Hossein Mousavi as he tries to mobilize Iran's youth.
There is an account (http://www.facebook.com/home.php?#/pages/Mir-Hossein-Mousavi-/45061919453) on Facebook in the name of Mousavi which claims over 6,600 supporters, besides a number of other accounts that are mobilizing support for the candidate.
Some reports from Iran suggest that the ban on Facebook may have been lifted. Other bloggers and users of Twitter in Iran are worried that these services may also be cut off.