21 March 2015, 12:38 GMT
"A mine exploded under their vehicle," defense ministry spokesperson Belhassen Oueslati told Agence France-Presse.
The incident comes just days after Islamist militants killed 20 foreign tourists and a policeman at the country's national museum on Wednesday.
Tunisia is currently hunting a third suspect implicated in the massacre, President Beji Caid Essebsi said on Sunday, after admitting security failures at the Bardo.
Wednesday's attack on the National Bardo Museum was the first assault claimed by the Islamic State group in the North African country.
