Customs agents were sacked after some were found to be linked to contraband operations, according to sources at the ministry.

Agents in Nuevo Laredo, on the border with the southern US state of Texas, were called in Saturday to be told they were fired, and to hand in their badges and weapons. A total of 1,100 agents were sacked, Mexican media said.

Army troops took over customs border posts temporarily on Sunday.

Mexico and the United States share a border that stretches across some 2,000 miles (3,220 kilometers) and are partners with Canada in the North American Free Trade Agreement (NAFTA).

Mexico is in the midst of a raging war on organized crime, and has expressed serious concern about US weapons crossing into the country.

During a visit to Mexico last week, US President Barack Obama praised President Felipe Calderon for his controversial military crackdown on the country's drug gangs, which involves more than 36,000 troops.

The United States has pledged around 1.6 billion dollars to tackle drug trafficking in Mexico and Central America under the Merida Initiative, which also includes funds for training and equipment to boost security on the Mexican side of the border.

The Obama administration has acknowledged the US role in the violence, pledging to stem the flow of weapons into Mexico and curb demand for drugs in the United States, one of the world's top cocaine consumers.