An explosion has hit a bus carrying presidential guards in Tunisian capital Tunis, killing at least 12 people, officials say.
President Beji Caid Essebsi has declared a 30-day state of emergency and the capital is under curfew.
No group has yet said it was behind the attack.
Tunisia has been targeted by the Islamic State group, including an attack by a gunman on the beach resort of Sousse in June, killing 38 people.
The North African state is believed to be the biggest exporter of jihadis, with the authorities saying at least 3000 of its nationals are fighting in Iraq and Syria.
The explosion happened at a bus stop where the presidential guard picks up and drops off its staff, near the former headquarters of the party of deposed President Zine El Abidine Ben Ali.
Roads in the city were already clogged because of heavy rain and flooding when the explosion hit.
Exactly what caused the blast is unclear but one source told Reuters a bomber had probably detonated explosives in the vehicle.
Mr Ben Ali was ousted in a popular uprising in 2011.
Tunisia currently has a secular government, which is battling the militants.
In March, gunmen attacked the famous Bardo Museum in Tunis, killing more than 20 people.