Tunisian President Moncef Marzouki has extended a state of emergency, which grants police special powers of intervention, until February 1, 2013, the official TAP news agency said.
"Marzouki decided on Wednesday to extend the state of emergency by three months from November 1, 2012," TAP said.
The three-month extension was proposed by military and security officials, it added.
Extensions of the state of emergency, which has been in place since January 2011, have only been made for 30 days at a time since July.
Wednesday's announcement will likely raise fears of a deteriorating security situation in Tunisia, which is still dealing with instability unleashed by the revolution that ousted long-time president Zine El Abidine Ben Ali in January 2011.
Tunisia has been shaken in recent weeks by a series of attacks by salafists. Police and soldiers were deployed in large numbers in the Tunisian capital after Tunisia's state news agency said one protester was killed and three security officers injured in clashes near Tunis on Tuesday.
Wielding sharp tools and swords, the protesters went on the attack in the Tunis suburb of Manouba after police arrested a Salafist suspected of assaulting the head of the suburb's public-security brigade, Khaled Tarrouche, interior ministry spokesman, said.
The authorities have vowed to crack down on violence in the wake of a salafist-led attack on the US embassy in September in which four assailants were killed.