Islamist militants have killed 24 Algerian paramilitary policemen - in one of the worst single attacks this year, according to reports.
They were ambushed near the settlement of Mansoura, east of the capital, said Algerian newspapers. The convoy was reportedly escorting Chinese workers.
There has been no official confirmation of the incident.
Algeria's militants, many veterans of the 1990s civil war, operate under the name al-Qaeda in the Islamic Maghreb.
The ambush - reported by the En-Nahar and Echourouk newspapers, and confirmed by unnamed local sources to the AFP and AP news agencies - is said to have occurred late on Wednesday.
The paramilitary police were reported to be escorting Chinese contractors to a motorway project; it is not known if any of the workers were injured.
The attackers had planted two improvised devices on the road 200km (124 miles) east of the capital, Algiers, and then opened fire on the convoy as the explosives went off, said reports.
The insurgents are said to have escaped, taking with them weapons and six off-road vehicles.
The BBC's Christian Fraser in Cairo says the roads heading east from Algiers into the rugged, mountainous parts of the country are a notoriously dangerous place to be.
Overall the number of attacks in Algeria appears to be in decline, but in recent weeks there has been a sudden spike, he adds.
The insurgents killed five paramilitary policemen late in May and a week later shot dead nine soldiers.
Earlier this month al-Qaeda in the Islamic Maghreb, also known as al-Qaeda in North Africa, killed a British man, Edwin Dyer, who they had abducted in January from Niger.