Security measures were tightened at Tunisia's polling stations on Sunday following a dawn attack in the central province of Kairouan that left one assailant dead and one solider wounded.
A man armed with a hunting rifle and three others reportedly attacked soldiers guarding ballot papers in the province's town of Haffouz for the country's presidential vote being held on Sunday.
The soldiers shot and killed the man and captured the three others, according to Defence Ministry spokesman Belhassan Oueslati.
Oueslati said he did not believe that militants, who had called for a boycott of Sunday's landmark election runoff and threatened to target the political establishment, were behind the attack.
"Generally, the terrorists don't use hunting rifles," he said.
After the incident, security authorities deployed some 100,000 troops to polling stations, with a focus on the country's western provinces.
At least 20 security units were deployed around five polling stations in the central city of Sidi Bouzid, an Anadolu Agency correspondent reported.
Similar deployments took place in the various cities and towns across the country, according to several AA correspondents.
Tunisia's Independent High Authority for Elections on Sunday delayed the opening of around 100 polling stations in the country's western regions until 10am (9am GMT), citing security reasons.
In an Internet video posted Wednesday, militants claimed the 2013 murder of two secular politicians, Mohamed Brahmi and Chokri Belaid, that plunged Tunisia into crisis, warning of more killings of politicians and security forces.