Iran is to have presidential elections in June. Elections in 2009 were marred by violence following a disputed claim to victory by President Mahmoud Ahmadinejad.
Iranian Intelligence Minister Heidar Moslehi said his agency was watching for signs of subversion ahead of the June vote.
"The intelligence ministry is conducting heavy monitoring in this regards," he was quoted by the semiofficial Fars News Agency as stating.
Moslehi said there were no signs of trouble so far, though Supreme Leader Ali Khamenei warned last month's that Iran's adversaries may try to undermine the vote.
Former Iranian Foreign Minister Manouchehr Mottaki this week announced he was running for president.
Khamenei in early 2011 tried to block Ahmadinejad from dismissing Mottaki.
Ahmadinejad is ineligible to run because of term limits.