At least 21 people were killed in a gunfight between armed civilians and the Mexican security sources near the U.S. border in northern Mexico, according to local media on Sunday.

An hour-long gun battle took place in Villa Union, a town in Coahuila state, Miguel Angel Riquelme, the state governor told local media.

Riquelme said the armed assailants attacked the local administration offices and federal security forces responded immediately.

A total of 21 people, including four policemen, lost their lives in the incident.

The armed assailants are thought to be alleged members of the Cartel of the Northeast

Read more: Mexico: 21 killed in gunfight near US border