There was no immediate claim of responsibility, but militants believed linked to the Islamic State carried out two major attacks past year in Tunisia targeting the country’s important tourism industry.
Monday’s attack came weeks after a USA airstrike killed almost 40 people at an Islamic State training camp in the Libyan city of Sabratha, near the Tunisian border.
Tunisia was targeted a year ago by three attacks that left 70 people dead and were claimed by IS.
President Beji Caid Sebsi denounced Monday’s attacks on police and army posts near his country’s border with Libya.
It is unclear if ISIS was at all involved in today’s incident, but Libya has a huge number of different factions, many hostile toward the Tunisian government, so it would be a mistake to label it obviously ISIS.
Tunisia’s government says the death toll in clashes between gunmen and security forces in a town bordering Libya has risen to 53.
Authorities have asked residents in Ben Gardane to stay indoors and report any suspicious activity.
Gunmen apparently crossing from Libya attacked a Tunisian border garrison on Monday, officials said, raising worries about Islamic State fighters and other militants gaining greater footholds in North Africa.
Hospital official Abdelkrim Chafroud said a 12-year-old was among the dead civilians, and two security agents were also killed. They also closed the main road north to the rest of Tunisia, the correspondent said. “The search continues”, said his spokesman Yasser Mesbah, adding that even in the town of Ben Guerdane “the situation is stable”.
U.S. commanders say such strikes are part of an effort to contain the spread of the Islamic State, while the United States and its allies consider a much wider campaign of airstrikes against the group in Libya.
Monday’s clashes took place as militants divided into groups launched consecutive attacks at police and army premises in Ben Gardane.
In a separate communique, French Foreign Minister Jean-March Ayrault denounced the attack which “only heightens the urgent need for a political solution in Libya”.
Last week, Tunisian security forces killed five heavily armed men in an hours-long firefight after they crossed into the country from Libya with a larger group.
On February 29, British Defence Minister Michael Fallon announced the deployment of 20 soldiers from the 4th Infantry Brigade to help train Tunisian border troops.
According to a United Nations working group on the use of mercenaries, more than 5,000 Tunisians have travelled overseas to join jihadist groups, many of them in Libya.