Iran’s decision to block access to Facebook - less than three weeks before nationwide elections - drew sharp criticism Sunday from a reformist opposition hoping to mobilize the youth vote and unseat President Mahmoud Ahmadinejad.

The decision, critics said, forces Iranians to rely on state-run media and other government sources ahead of the June 12 election.

It also appeared to be a direct strike at the youth vote that could pose challenges to Ahmadinejad’s re-election bid.

More than half of Iran’s population was born after the 1979 Islamic Revolution and young voters make up a huge bloc - which helped former reformist President Mohammad Khatami to back-to-back victories in 1997 and 2001 but failed to rally strongly behind Ahmadinejad’s opponent, Akbar Hashemi Rafsanjani, four years ago.

Young voters are now strongly courted by the main reformist candidate, Mir Hossein Mousavi, as the possible swing factor.

“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, the leading reformist candidate. “Placing limits on the competition is the top priority of the government.”