Mexican authorities say at least 13 people were killed in two shootouts between troops and gunmen in northern Mexico.

An army official who spoke on condition of anonymity because he is not authorized to speak to the media says all those killed were gunmen working for the Zetas drug gang.

The northern Mexian newspaper El Norte reported that at least one bystander was killed.

The official says troops were searching a villa in the Juarez suburb of Monterrey on Friday when they were ambushed by heavily armed men. The official says 10 gunmen were killed in that shootout.

He says some gunmen fled in cars and were killed during a second shootout near the town's center.