According to BBC, officials said three officers were attacked by two men on a motorcycle.
The interior ministry said police in the city, 140km south of the capital Tunis, had launched a vast search for the gunmen.
Tunisia's tourism industry has suffered badly since the Sousse beach killings and an attack in Tunis in March. BBC reports.
"Three policemen were the target of gunshots fired by two men on a big motorcycle," a statement from the interior ministry said.
"One of them died during transport to the hospital, the other two were not affected," it added.
Officials say more than 3,000 Tunisians have left to fight with IS in Iraq and Syria and increasingly in neighbouring Libya.
The gunmen in the Sousse massacre and an attack on the Bardo Museum in Tunis on 18 March were trained in militant camps in Libya.