Fifteen people have been killed in a clash between Islamist militants and Algerian security forces in the eastern region of Batna, local media report.
The attacks happened 450km east of the capital Algiers
The militants carried out a rocket attack on an army post, killing five soldiers, while 10 Islamists reportedly died in an army counter-attack.
A BBC correspondent in Algeria says this is the most serious Islamist attack for several months.
They are thought to belong to a group now renamed "al-Qaeda in the Maghreb".
Earlier this week, the Salafist Group of Preaching and Combat (GSPC) announced that it had changed its name.
This latest clash comes amid repeated calls by the army to the general population to help them in their fight against armed militants.
The army has put up posters across north-central Algeria, urging people to give them any information they had about "terrorists".
It is the first time since the start of the violence linked to radical Islamists in 1992 that the army has used this method of gathering information on the militants.
The BBC's Mohammed Arezki Himeur in Algiers says the extensive use of posters by the army contrasts with the government's insistence that armed Islamist groups have been defeated with no chance of resurgence.
Last August, Algeria offered Islamic militants a six-month amnesty on condition of surrender, but fewer than 300 came forward.
Militants were promised immunity from prosecution provided they were not involved in serious crimes such as massacres, rapes and bombings.