Tunisia has identified three suspects wanted over Tuesday's suicide bombing that killed 12 presidential guards and is offering a financial reward for information leading to their arrest.
The interior ministry issued a statement on Friday evening identifying the men as Hassan Ben Khalifa Bouchiba, Houcine Ben Khalifa Bouchiba and Walid Ben Mohamed Ali Yousfi.
An initial probe has proven that these "terrorist elements... (are) linked to the explosion on a bus of the presidential guard," the statement said.
The ministry also promised "an important financial reward" for "anyone providing information leading to the arrest" of the three suspects.
Tuesday's suicide bombing in the centre of Tunis was claimed by the Islamic State group, and authorities have identified the bomber as 26-year-old Tunisian travelling salesman Houssam Abdelli.
Authorities said he had been detained in August on suspicion of being an extremist. A search of his house turned up religious books that were deemed to be harmless, and he was released without charges.
However, the prosecution decided that he should be kept under surveillance but it is not clear if any surveillance was ever carried out. The police report into the August incident only reached the prosecutor's office on Thursday, two days after the attack.
The interior ministry said Saturday it had carried out hundreds of searches and arrested dozens of people since the attack, of whom "41 people suspected of belonging to terrorist organisations" were detained overnight.
ISIS also claimed responsibility for two attacks earlier this year at the National Bardo Museum in Tunis and on a hotel near the Mediterranean resort of Sousse that killed a total of 60 people, all but one of them foreign tourists.
The secretary of state for national security, Rafik Chelly, told private Mosaique FM radio that all these attacks were planned in neighbouring Libya.
Tunisia, the cradle of the Arab Spring uprisings, has been plagued by Islamist violence since the 2011 overthrow of longtime dictator Zine El Abidine Ben Ali.
IS has exploited the chaos that spread across Libya since the 2011 revolt that toppled and killed veteran leader Moamer Kadhafi to gain a presence in the oil-rich North African state.