The truck was carrying 19 guards on their way to take part in a security force "mopping-up operation" against Muslim fighters on Tuesday.
It was blown up on a track near the village of Ain Rich, 180km southwest of the town of M'Sila, the newspapers said.
Twelve communal guardsmen died on the spot, a thirteenth dying later on the way to hospital.
Algeria's El-Watan daily quoted one of the wounded guards as saying: "No terrorist appeared at the scene of the attack."
The armed fighters operating in the Ain Rich region belonged to the Salafist Group for Preaching and Combat (GSPC), the state-funded newspapers said.
The last GSPC attack in the region cost the lives of two soldiers in March.
The Ain Rich blast was the deadliest incident in Algeria since 15 May when 12 troops were killed in the Khenchela region, 500km east of Algiers, in an ambush attributed by the press to the GSPC.
On 21 February the GSPC announced it had killed 10 soldiers three days earlier in an ambush of a convoy in the Batna region, 430km east of the capital.
President Abdelaziz Bouteflika
says violence has diminished
The GSPC also claimed an attack on Saturday against a military base in northeast Mauritania.
The Mauritanian government said 15 people were killed and 17 injured in the raid on the base by about 150 assailants in the isolated desert Lemgheitty region.
Algeria's civil war started in 1991 when the army annulled elections that an Islamic party was poised to win.
More than 100,000 people are thought to have died in the conflict.