The strike is the second in its history, highlighting the government's continued crackdown on freedom of expression in Tunisia.
A Tunisian journalist was detained on Friday for accusing the public prosecutor on television late last month of fabricating evidence implicating a cameraman in an egg-throwing attack on a minister, prompting a union call to strike.
The cameraman, Mourad Meherzi, is on trial for complicity in the egg attack on Culture Minister Mehdi Mabrouk.
Meherzi, who spent three weeks in detention before being released on bail last week, insists he was merely doing his job in recording the incident, with Nasreddine Shili, the film-maker who hurled the egg, vouching for him.
The minister's lawyer acknowledged last week that Meherzi was only doing his job, being at the scene of the incident, but the cameraman is still on trial and Shili remains in custody.
Heni's lawyer Moufida Belghrith told AFP, "The committal order was given even before our statements and the questioning of Heni. This detention is illegal."
Several dozen journalists and lawyers prevented police from executing the order by blocking access to the judge's office. But the security forces finally managed to detain Heni, who was led away in a police convoy amid shouting from protesters.
Another of Heni's lawyers, Abdelaziz Essid, said he could be released on bail of 2 000 dinars, but not before Monday morning.
Continued pressure on media
The national union of Tunisian journalists called a general strike, only the second in its history, in protest against Heni's detention and to denounce pressure on the media by the Islamist-led government. It also urged the country's media to boycott "all the activities of government".
Just hours after his arrest, Heni renewed his accusations despite the risk of being jailed. "I am going to present to the judge two documents that prove what I have declared about the allegations of the public prosecutor Tarek Chkioua," he said on his Facebook page.
"Chkioua argued that the detention of my colleague Mourad Meherzi was decided on the basis of confessions about his involvement in a plot to attack the minister of culture," Heni added. "There is no proof. On the contrary, (Meherzi) has even refused to sign the statement (following his interrogation). I will ask that Tarek Chkioua is tried for placing someone in detention without any legal basis."
Heni was a fierce critic of Zine El Abidine Ben Ali, Tunisia's former strongman toppled in Tunisia's mass uprising in January 2011 that unleashed the Arab Spring. But he was never imprisoned, despite constant police harassment.
Since the revolution, he has regularly accused the Islamist party Ennahda, which heads the coalition government, of manipulating the courts and security forces for political ends.
Calls for freedom of expression
The country's powerful Tunisian General Labour Union (UGTT) on Friday strongly criticised attacks on the freedom of expression.
"(UGTT leader Houcine) Abassi expresses his astonishment over the successive trials of journalists and voices his concern. This sector is unable to evolve in light of these attempts to make it submit," the UGTT stated.
Human Rights Watch (HRW) has also slammed the government over the prosecution of journalists for expressing their opinions, citing the case of Heni and another journalist, Zouhaer al-Jiss. Since early 2012, HRW said the authorities have used the same "repressive legal arsenal" to stifle free speech that was employed under the Ben Ali regime, and that "numerous journalists, bloggers, artists, and intellectuals have been prosecuted".
The attack on the culture minister took place at a memorial ceremony on August 16 marking 40 days since the death of a fellow artist, with Meherzi filming the attack and the images subsequently broadcast by Astrolab TV, for whom he was working.
The act was reportedly in protest at the inadequate response by the minister, an independent in the Islamist-led coalition government, to attacks on artists by extremists who deem their work offensive. – Sapa