At least 21 people have been killed in a gun battle between two of Mexico's most powerful drug gangs, the Sinaloa and an offshoot known as the Beltran Layvaa.

Police said the violent showdown took place 20km from the Mexico-US border, near the city of Nogales.

The authorities have arrested nine people, six of whom were wounded in the clash.

Al Jazeera's Mariana Sanchez reports. (July 03, 2010)