Suspected Islamist militants in northern Algeria have killed 13 local government guards, media reports say.
The guards were travelling in a lorry when it was blown up by an explosive device in the region of M'sila, south-east of the capital, Algiers.
They were part of an operation to clear Islamist militants from the area.
Algerian press sources say fighters of the Salafist Group for Preaching and Combat (GSPC) are to blame. The group is fighting for an Islamic state.
The GSPC is Algeria's largest and best organised armed group.
It is behind the majority of terrorist acts committed in Algeria - including an attack on Sunday on a military base in neighbouring Mauritania that left 15 soldiers dead.
Militant attacks have been blamed for the deaths of more than 80 people in Algeria since the beginning of May.
Unlike other militant groups, the GSPC - which is allegedly affiliated to Osama Bin Laden's al-Qaeda network - prefers to target members of the security forces, and not civilians, says the BBC's Mohamed Arezki Himeur in Algiers.
In a communique released after the Mauritania attack, the group warned that it would not cease its attacks on its enemies either inside or outside Algeria.
Militant Algerian groups have waged a decade-long campaign of violence, following the annulment in 1992 of elections which Islamic groups were poised to win.
An estimated 150,000 people are thought to have been killed in the violence.