May 23 (Bloomberg) -- Iran blocked social networking Web sites Facebook and Twitter before the June 12 presidential elections, the technical officer of Internet service provider Aryasat said.

The Web sites were blocked as of 3 p.m. in Tehran today, Massoud Sharififar said in a telephone interview. The country’s Ministry of Telecommunications operates a system to block Web sites in accordance with the judiciary, Sharififar said.

Candidates opposing President Mahmoud Ahmadinejad and their supporters have used the sites as part of their campaigns.

“Our media reach is very limited,” said Mohammad Ali Abtahi, who served as a vice president between 2001 and 2004 under former president Mohammad Khatami. He said that Ahmadinejad gets much of the coverage on state television. Abtahi is now a senior adviser to so-called reformist candidate Mehdi Karrubi.

Supporters of Mir-Hossein Mousavi, who has the backing of many university students and young Iranians, have used the networking sites to distribute information.

Facebook is investigating the reports, spokeswoman Debbie Frost wrote today in an e-mail.

“We are disappointed to learn of reports that users in Iran may not have access to Facebook, especially at a time when voters are turning to the Internet as a source of information about election candidates and their positions,” she wrote.

The Twitter press office didn’t return an e-mail left earlier today seeking comment.

To contact the reporter on this story: Ali Sheikholeslami in London at Alis2@bloomberg.net.

Last Updated: May 23, 2009 16:24 EDT