Access to the popular social networking Web site Facebook is back in Iran after being blocked late last week.
Facebook was cut off Saturday, leading to accusations that authorities were trying to muzzle one of the main campaign tools of reformists opposing President Mahmoud Ahmadinejad in June 12 elections.
The main pro-reform candidate, Mir Hossein Mousavi, is seeking a strong turnout from young voters and has used Facebook to try to mobilize support.
Authorities have not directly commented on the Facebook outage, and the reason for its return Tuesday was not immediately clear.
It also was not known whether the renewed Facebook access is permanent. Iranian authorities have restored then re-imposed blocks on Web sites in the past.
When Iran blocked access to Facebook on Sunday, government critics condemned the move as an attempt to muzzle the opposition ahead of next month's presidential election.
Blogs and web sites such as Facebook have become an important campaign tool for the leading reformist candidate, Mir Hossein Mousavi, to mobilize Iran's critical youth vote before the June 12 balloting.
Iranian authorities often block specific web sites and blogs considered critical of the Islamic regime, but the timing of the latest clampdown suggested it was done to hobble opponents of hardline President Mahmoud Ahmadinejad.
"Every single media outlet that is seen as competition for Ahmadinejad is at risk of being closed," said Shahab Tabatabaei, a top aide for Mousavi. "Placing limits on the competition is the top priority of the government."
Tabatabaei said the Facebook block was "a swift reaction" to a major pro-Mousavi rally Saturday in a Tehran sports stadium that included an appearance by former reformist president Mohammad Khatami and many young people waving green banners and scarves — the symbolic color of the Mousavi campaign.
"Facebook is one of the only independent sources that the Iranian youth could use to communicate," said Mohammed Ali Abtahi, a former vice president and now adviser to another pro-reform candidate, Mahdi Karroubi, a former parliament speaker.
Abtahi said that without Facebook — and possibly other web sites popular with reformists — Iranians would be "forced to rely on government sources" such as state-run media.
Ahmadinejad is in a four-way race for re-election against the two pro-reform candidates and fellow conservative Mohsen Rezaei.
The Internet and other technology have increasingly become part of Iranian political movements in the past decade.
During the last presidential race in 2005, information about rallies and campaign updates were sent by text message. In recent years, political blogs by Iranians in the country and abroad have grown sharply. Newcomers such as Twitter also are gaining in popularity.