Iranian censors have blocked access to a number of news websites sympathetic to President Mahmoud Ahmadinejad, adding further fuel to a high-level power struggle at the heart of the Islamic regime.

Authorities in charge of online censorship in Iran, who are believed to be close to the country's supreme leader, Ayatollah Ali Khamenei, and his powerful Revolutionary Guards, have in the past few days filtered a series of websites and blogs which were operating in support of Ahmadinejad and his allies.

The move comes ahead of parliamentary elections in March, described as the most sensitive in the history of the Islamic republic.

Digarban, an opposition website which monitors the activities of conservatives inside the regime, has identified a list of pro-Ahmadinejad websites blocked recently, including mahramane.com and www.rahapress.com.

Last year, it emerged that a rift had developed between Khamenei and his supporters on one side and Ahmadinejad and his allies on the other, each fighting for greater share of power over Iranian politics.

Opponents of Ahmadinejad accused him and his close confidant and chief of staff, Esfandiar Rahim Mashaei, of attempting to undermine the clerical power and supremacy of Khamenei by advocating nationalistic causes in order to appeal to a larger number of Iranians.

Dozens of Ahmadinejad's allies have been arrested in recent months and media adviser Ali Akbar Javanfekr, one of his top aides, this week lost an appeal against a six-month jail term.

But Iran's parliamentary elections, scheduled for 2 March, are seen as an opportunity for Ahmadinejad to fight back.

The current parliament, which is dominated by Khamenei's people, has been critical of Ahmadinejad and has repeatedly threatened him with impeachment. In an unprecedented move, the parliament last week summoned Ahmadinejad to answer a series of questions over the government's handling of the economy and his personal judgments. Ahmadinejad has one month to appear before the parliament.

Iran's opposition and reformists have largely boycotted the coming poll, which will be the country's first elections since 2009, leaving it open for Ahmadinejad's team to oppose pro-Khamenei conservatives.

The Guardian Council, which vets all candidates before any election, has not yet announced the final list of those allowed to run but many analysts believe Ahmadinejad's allies are likely to hide their allegiances in order to avoid being barred. The council has delayed its announcement of the final list of approved candidates in an apparent move to allow little time for opponents to voice discontent.

The March vote, described by Iran's intelligence minister, Heidar Moslehi, as "the most sensitive" in the history of the Islamic republic, comes at a time when the regime is facing economic discontent at home and increasing international isolation because of western sanctions imposed after a dispute over the country's controversial nuclear activities.

The rhetoric between Iran and Israel has escalated over allegations about bomb attacks in capitals including Delhi, Tbilisi and Bangkok. Many analysts doubt that Tehran's foreign policy is controlled by Ahmadinejad's government and attribute it to Khamenei and his elite Revolutionary Guards.

Iran launched a fresh clampdown on web users last month, with draconian rules on cybercafes. In the past week, Iran has reacted to calls for fresh street protests over the house arrest of opposition leaders Mir Hossein Mousavi and Mehdi Karroubi by reducing internet speeds significantly and temporarily blocking access to emails.