Two workers were also injured in the accident, which saw a 30 metre (100 foot) long section of the six metre (20 foot) high walls near the Gate of the Floggers crash to the ground, the Civil Protection department said.
"A team was carrying out restoration work" on the three kilometre (two mile) long wall that surrounds the Old City, department spokesman Moez Tria told AFP, adding that the accident "could be linked to heavy rains in the area in recent days".
Founded in 670 AD, Kairouan is one of North Africa's holiest cities and a leading tourist attraction. It has been listed as a UNESCO World Heritage Site since 1988.
