Since the fall of Saddam Hussein, Iraqi media have flourished
About 200 Iraqi journalists, writers and publishers have protested in Baghdad at what they say is growing state interference in their work.
The protest follows the introduction of new rules for censoring books, and a proposal to ban certain websites.
Some journalists say there has been an increase in lawsuits against those investigating security or corruption.
The authorities say they will only block websites that are pornographic or incite violence or criminal behaviour.
Media workers have frequently been targeted or caught up in the violence in Iraq, with at least 190 being killed since the US-led invasion in March 2003.
Dozens of journalists took part in the demonstration at Baghdad's old book market on Friday, carrying signs which read "Do not kill the truth", and chanting "Yes to freedom. No to silencing journalists".
"It is the very duty of journalists to reveal the truth, and we are against any kind of censorship of the media," said Deputy Culture Minister Fawzi al-Atroushi, who attended the rally.
"We are against any threats made against journalists."
Last year, as security improved and the national government began to gain strength, journalists started to complain about new pressure from the officials.
The Association for Protection of Journalists says there has been a dramatic increase in lawsuits against media workers, especially those who try to cover government corruption and security.
Recently, a Shia MP threatened to sue over an editorial suggesting an unnamed political party had supported a bank robbery in Baghdad in July in which $7m was stolen and eight security guards were killed.
It came after a bodyguard of Vice-President Adel Abdul-Mahdi, a senior leader of the Supreme Iraqi Islamic Council, was arrested in connection with the crime.
Representatives of the publishing industry, who attended Friday's demonstration, are concerned about the recently imposed book censorship laws.
There has also been much criticism by freedom of speech advocates of the government's proposal to crack down on internet service providers and ban websites that incite violence and publish pornography.
Earlier this year, Prime Minister Nouri Maliki told reporters to be more co-operative and less critical of the government.
The BBC's Natalia Antelava in Baghdad says it was a disturbing statement for those who lived, for years, without any freedom of expression.
Since the fall of Saddam Hussein, Iraqi media have flourished, and many journalists would often say that physical danger was a trade-off for their newly found freedom to report, our correspondent says.
They fear their freedom is now under threat, she adds.