Two Turkish journalists could be sentenced to four and a half years in jail after publishing the cover of French satirical magazine Charlie Hebdo that depicted the Prophet Mohammed.

The two columnists, Ceyda Karan and Hikmet Cetinkaya, work for the pro-secular Cumhuriyet newspaper. They were charged with "inciting public hatred" and "insulting people's religious values", AP reported.

Cumhuriyet published a selection of Hebdo's images shortly after the magazine was attacked by Islamist gunmen who claimed they belonged to the al-Qaeda terror group. Ten Charlie Hebdo staff and two policemen were killed in the attack.

Following the massacre, Hebdo published a 'survivors' edition' which featured Prophet Mohammed on the cover, enraging thousand of Muslims whose religion forbids the depiction of religious figures.

Although Cumhuriyet did not publish the image of the Prophet, Karan and Cetinkaya included it in their columns, prompting prosecutors to launch an investigation after Prime Minister Ahmet Davutoglu said his government would not allow "insults to our Prophet".

Karan told Reuters: "We are being threatened with prison for defending free speech. To threaten a journalist because he or she printed a drawing that does not include an insult can only come from a religious, authoritarian government.

"Neither of us will abandon our defence of free speech."

The current Turkish government has been often accused of curbing freedom of speech. The country ranked 152 in the 2014 World Press Freedom Index, having dropped 20 positions from the 132th place it gained in the 2010 index.

President Recep Tayyip Erdogan is also accused of trying to replace secularism values with Islamist ones.

Turkey is facing backlash on social media censorship after blocking Twitter and YouTube following the publication of an image of a Turkish prosecutor, Mehmet Selim Kiraz, being held as a hostage. He was later killed.