Gunmen attacked a convoy of customs agents traveling through the desert in southern Algeria on Friday, killing 13 and wounding eight others, the official APS news agency reported. One other person was reported to have disappeared in the attack in the Ghardaia region, 745 miles south of the capital of this North African nation, APS reported, citing local security sources. The attackers opened fire with machine-guns on vehicles transporting the customs agents to a seminar, then set the vehicles afire, according to a report on daily Liberte's Web site. The gunmen, whose numbers were not immediately known, then fled in two four-wheel drive vehicles.