Tunisia's Islamist premier Ali Larayedh vowed tough action against Ansar al-Sharia on Monday after bloody clashes between police and members of the radical Salafist group, hinting at a shift in government policy.

Tunisia has been rocked by waves of violence blamed on militant Islamists since its January 2011 revolution, and Larayedh reacted angrily to the latest unrest, which erupted after the authorities banned the group's annual congress.

At least one protester was killed and 15 police hurt, with victim due to be buried later on Monday in Ettadhamen, the poor Tunis suburb and renowned Salafist stronghold where Sunday's clashes broke out.

Ansar al-Sharia and a police source said a second protester was also killed, but the interior ministry said his death was not linked to the clashes, while the Salafists insisted neither victim belonged to their movement.

Larayedh said around 200 Salafists were arrested and vowed firm action against the group considered close to Al-Qaeda that he linked for the first time to "terrorism," prompting analysts to see a possible shift in government policy.

"Those proven to have nothing against them will be released, but those found to have been involved in violating the law will be prosecuted," he told AFP during a visit to Doha.

"Ansar al-Sharia is an illegal organisation which defies and provokes state authority," Larayedh told Tunisian state television last on Sunday.

"It has ties to and is involved in terrorism," added the former interior minister and stalwart of the ruling Ennahda party.

The moderate Islamist party has been sharply criticised for failing to prevent a surge in attacks by hardline Islamists since the mass uprising that toppled Zine El Abidine Ben Ali, and of being too lenient towards the Salafists.

But faced with the threat of two armed jihadist groups hiding near the Algerian border, it has hardened its stance, banning the Salafists' planned congress on Sunday in the holy city of Kairouan after their leader threatened "war" against the government.

Analysts say the prime minister's comments late on Sunday may signal a turning point.

"It is a change of language. Larayedh has never before used this term for Ansar... reserving the word terrorist for the groups" which Tunisia's army is hunting on the Algerian border, said Michael Ayari from the International Crisis Group think-tank.

It remains to be seen whether the premier's words will be followed by actions, with Ayari pointing out that dozens of Salafists were arrested after an attack on the US embassy in September and most of them freed several months later.

"The words count, but we still can't say that the policy has changed, that they mark a point of no return, and that the Ansar al-Sharia activists will now be arrested for belonging to the movement, for their political identity," he added.

But Ansar al-Sharia's leader Abu Iyadh, a former Al-Qaeda fighter in Afghanistan whose real name is Saif Allah Bin Hussein, was defiant in a message posted online Sunday, apparently taped before the day's violence.

"God knows well that I would like to have been with you at the moment when you opened a shining page in the history of our nation. You have shown the entire world that your efforts cannot be defeated despite the persecution of your leaders," he said.

The audio recording was posted on the group's Facebook page.

Abu Iyadh has been on the run since September, after the attack by Islamist protesters on the US embassy in Tunis that he is accused of having orchestrated and which left four assailants dead.

Salafists advocate an ultra-conservative brand of Sunni Islam, and they have benefited from the regional security vacuum that accompanied the Arab Spring uprisings.

Ansar al-Sharia is considered the most radical of the extremist groups that have emerged in Tunisia since the 2011 revolution.