At least 12 people were killed on Tuesday when an explosion tore through a bus full of Tunisian presidential guards in an attack that one source said was probably the work of a suicide bomber.
Ambulances rushed wounded from the scene and security forces closed off streets around Mohamed V Avenue, one of the main streets in the capital Tunis, where the charred wreckage of the bus lay, not far from the Interior Ministry.
It was the third major attack in Tunisia this year, after an Islamist militant killed 38 foreigners at a beach hotel in the resort of Sousse in June, and gunmen killed 21 tourists at the Bardo Museum in Tunis in March.
Fighting Islamist militants has become a major challenge for Tunisia, a small North African country that was hailed as a blueprint for democratic change in the region after an uprising in 2011 ousted autocrat Zine Abidine Ben Ali.
