Tunisia’s banned group Ansar al-Sharia designated a "terrorist organization" by the authorities, has called for a demonstration Tuesday in central Tunis to mark the third anniversary of the revolution.

Tunisia's banned group Ansar al-Sharia designated a "terrorist organization" by the authorities, has called for a demonstration Tuesday in central Tunis to mark the third anniversary of the revolution.

"The struggle is mandatory and it must be a popular struggle... which is why we extend our hands to anyone wanting to stand up to repression and we support the planned protest at the Kasbah on Tuesday," the group said on its official Facebook page.

"We must struggle against the tyranny of the authorities by all means possible," added the group, which is blamed for killing two leftist opposition MPs in separate attacks earlier this year.

It called on the people to carry with them "the anger of the orphans, the widows, the oppressed, the families of martyrs and detainees, and those who have suffered torture and oppression."

The authorities did not immediately respond to Ansar al-Sharia's call, which comes as Tunisia prepares to mark the third anniversary of the start of the revolution that toppled former strongman Zine El Abidine Ben Ali.

There have been numerous calls to protest at the Kasbah in Tunis, where the government's headquarters are located, across the Internet and on fly posters.

Opposition activists are also calling for a day of "rage" in the impoverished central town of Sidi Bouzid, where the self-immolation of 26-year-old street vendor sparked the first so-called Arab Spring uprising.

Since then, Tunisia has been rocked by violence blamed on banned groups that were suppressed under the former dictator, with attacks multiplying in recent months, and with the opposition blaming the ruling Islamist party Ennahda of failing to rein in the extremists.

The authorities say Ansar al-Sharia has ties to Al-Qaeda and was behind the killing of Chokri Belaid and Mohammed Brahmi in February and July, attacks which sparked political crises.

Ansar al-Sharia has denies responsibility for the Belaid and Brahmi murders.

Since the summer police have carried out multiple arrests aimed at weakening the secretive group, which accused Ennahda on Monday of being "traitors" only interested in power.