* News outlets have been critical of government
* 2009 vote prompted accusations of rigging, riots
* Authorities mindful of more protests (Adds report of two more arrests, lobby group statement)
Iranian authorities have arrested more than a dozen journalists in the past two days over their links to "anti-revolutionary" media, Iranian media reported, in what appeared to be a coordinated crackdown on the press.
With a presidential election five months away, Iran's clerical leadership appears to be tightening its grip on the media to avoid a repeat of the widespread protests that erupted after the disputed election in 2009.
Journalists working for reformist newspapers Arman, Bahar, Etemaad, Shargh, and the Aseman weekly - and Iran's economy-focused ILNA labour news agency - were arrested on Sunday for cooperating with Persian-language "anti-revolutionary" news outlets, Mehr news agency reported late on Sunday.
In Iran, anti-revolutionary means those who work against the Iranian leadership and its 1979 Islamic revolution.
The exact numbers were not known, but several outlets reported the arrests, with Fars news agency saying around 11 journalists were detained on Sunday on the orders of the judiciary. In addition, the opposition Kaleme website said a reporter for Bahar and one from ILNA were held on Saturday.
In a separate report later on Monday, Fars said two other journalists were arrested. The Fars report named the two men but did not say where they worked.
While not calling for outright dissent, the outlets have reported on an economy struggling under Western sanctions imposed over Iran's disputed nuclear programme, and often feature criticism of Iranian government policies.
Shargh was banned for several months in 2012 for publishing a cartoon deemed insulting to veterans of the Iran-Iraq war, while ILNA closely follows news of layoffs in Iran's factories - bad news for the leadership in the run up to June's election.
The economy has taken a battering since the introduction of U.S. banking sanctions a year ago that virtually severed links to the global financial system. Iranians have seen the price of food and goods soar and their spending power slump, especially on imports that are directly affected by the weakening rial.
Last week, Iran's judiciary spokesman Gholam Hossein Mohseni-Ejei warned of the threat the Islamic Republic faced from some of its own journalists.
"Based on information I have from reliable sources, unfortunately a number of journalists, as well as writing for the nation's newspapers, work hand-in-hand with Westerners and anti-revolutionaries," he said at the time.
The Iranian leadership regularly accuses Western governments of trying to foment social unrest through subversive media activities but says that such plans will never succeed.
However, the latest crackdown appeared to go further than just targeting reformist news organisations, with the conservative website Tabnak also offline on the orders of the Tehran prosecutor's office, the state body that determines which websites to filter told the ISNA news agency on Sunday.
Reporters Without Borders, which advocates press freedom, called on Monday for the "immediate and unconditional release of all journalists currently detained in Iran".
It said that in addition to those arrested over the weekend, other journalists had been sent summonses to appear before revolutionary courts in the coming days.
Opposition candidates Mirhossein Mousavi and Mehdi Karoubi said the 2009 election was rigged in favour of President Mahmoud Ahmadinejad. They have been under house arrest for nearly two years.
The government denied vote rigging and said the protests were stirred up by Iran's foreign enemies to overthrow the Islamic Republic's system of government.
Analysts say reformist candidates may be allowed to run this time if they distance themselves from Mousavi and Karoubi.
But the authorities are mindful of more protests, and hardliners have warned against the possibility of a second "sedition", the term officials use for the 2009 demonstrations.
Iran is one of the world's worst countries for jailing members of the press, along with Turkey and China, according to the Committee to Protect Journalists. A CPJ tally in December 2012 said there were 45 journalists behind bars in Iran.