MEXICO CITY - Eighteen people were killed in armed clashes between rival gangs in northeastern Mexico on Monday, local media reported.

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The violence occurred in central Abasolo, the Tamaulipas state, which borders the US state of Texas.

Drug trafficking violence is constant in Tamaulipas as the region's two competing drug groups, the Zetas and the Gulf cartels, have been battling for control of smuggling routes into the US market and local markets.

Earlier this year, in Padilla, another town of Tamaulipas, 18 people were killed in fighting in February.