US social networking site Facebook has said it had received reports its wesbite had been blocked in Iran, lamenting the apparent government bar as "a shame."
"We are disappointed to learn of reports that users in Iran may not have access to Facebook," the company said in a statement on Sunday.
One Iranian news agency reported earlier that the government had blocked access to Facebook ahead of June presidential polls, allegedly to prevent supporters of the leading opposition candidate from using the site for his campaign.
Facebook said it was investigating the reports, and expressed disappointment that the site was apparently blocked "at a time when voters are turning to the Internet as a source of information about election candidates and their positions.
"It is always a shame when countries' cultural and political concerns lead to limits being placed on the opportunity for sharing and expression that the Internet provides."
One Facebook page, dedicated to Mir Hossein Mousavi, a rival of the incumbent president Mahmoud Ahmadinejad, has more than 5,200 supporters.
Iranian state-controlled television and radio have already been the focus of debate over whether candidates will get equal treatment.