The announcement Thursday by the Interior Ministry comes as Tunisians are still reeling from clashes earlier this week between police and religious youth in the capital and other cities after protests erupted over an upscale art exhibit that hardline Islamists alleged was blasphemous.
Tunisians overthrew secular dictator Zine El Abidine Ben Ali last year in a popular uprising that sparked similar pro-democracy movements around the region. The old regime savagely repressed any manifestations of political Islam, and in its absence there has been an upsurge of new religious groups.
The growing tensions in Tunisian society now are not just between the religious-minded and secularists, however, but also between moderate Muslims and ultraconservative Islamists.
Two organizations of ultraconservative Muslims—Hizb ut-Tahrir and Ansar al-Shariah—called for renewed protests over the now-closed art exhibit following Friday prayers.
The leader of the moderate Islamist party Ennahda, whose members control the government, then called for a rival demonstration of party faithful to "protect the revolution." Ennahda is allied with two secular parties, and it has not pushed for the implementation of Islamic law.
But the Interior Ministry said none of the marches would be allowed, adding in a statement, "It has come to the attention of the ministry that certain unidentified parties plan to take advantage of the peaceful demonstrations to spread chaos."
Pressed for details, ministry spokesman Lotfi Hidouri said calls for violence have been circulating for several days in online forums, including Facebook. In the current tense environment, he said, "even peaceful demonstrations can become a platform for acts of violence and vandalism."
Late Thursday, Ennahda as well as Hizb ut-Tahrir and Ansar al-Shariah agreed not to hold large demonstrations due to the ministry's ruling. The hardline groups, however, will go ahead Friday with a small protest in front of the seat of government.
The rise of the religious right has horrified the country's secular elite, whom many of the Islamists see as having been complicit with the old regime and its harsh tactics. A number of intellectuals, including politician Nejib Chebbi and journalist Taoufic Ben Brik, said Thursday they had received death threats.
The artwork that spurred the latest clash was exhibited in the affluent Tunis suburb of La Marsa. The work included paintings caricaturing Mecca, portraying a nude woman, and showing the word "Allah" spelled with strings of ants.
Late on Sunday, hundreds of extremists attacked the exhibit. Mobs, believed to be followers of an ultraconservative strand of Islam known as Salafis, attacked police posts, art galleries and the headquarters of unions in several cities across the country over the next few days.
One person died after being shot in the head in the coastal city of Sousse on Wednesday.