MEXICO CITY (Reuters) - Fighting in a prison on Mexico's border with the United States has killed 20 people and wounded 12 others, authorities said on Saturday.

The violence broke out this morning following an altercation between two inmates in the prison in Matamoros, a northeastern city right opposite Brownsville, Texas, the government of Tamaulipas state said in a statement.

Guards at the Centro de Ejecucion de Sanciones de Matamoros (CEDES) penitentiary later restored order with the aid of police, the statement added. The Tamaulipas government gave no details of weapons involved or how the victims died.

Many Mexican prisons are overcrowded and often plagued by violence linked to the country's powerful drug cartels. Turf wars between gangs fighting for control of smuggling routes in border regions have been particularly brutal.

The incident in Matamoros was one of the most violent to hit the country's prisons this year.

Since President Felipe Calderon's government sent in the army to crush the drug cartels at the end of 2006, more than 44,000 people have died in the ensuing violence.

(Reporting by Miguel Angel Gutierrez)