The raids will cover Nuevo Laredo, a town across the border from Laredo, Texas, that has been bloodied by turf wars between drug gangs in recent years.

Officials also said that in the two months since intensive raids began in central and western Mexico they have destroyed almost as many opium fields as plots of marijuana, long Mexico´s principal drug crop.

"We have begun a frontal struggle against organized crime that has no precedent in the country´s history," said Interior Secre tary Francisco Ramírez Acuna. "We are recovering (Mexico´s) territory for our children," he said of the raids, which began Dec. 8 in the western state of Michoacán, and have since been expanded to several other states.

Starting over the weekend, 2,035 soldiers, 750 navy personnel and 516 federal police were dispatched to Tamaulipas - home to the border cities of Nuevo Laredo, Reynosa and Matamoros - and the state of Nuevo León, where shootings of police have become more common.

The federal government said the operation came at the request of the governors of those two states.

The raids in the two border states will focus on key points in the main trafficking routes, Defense Secretary Guillermo Galván told a news conference. In the past, that policy has meant setting up highway checkpoints to search cars and trucks.

Authorities announced they already seized hand grenades and clandestine drug labs during raids, which have occurred in the states of Michoacán, Guerrero, the border city of Tijuana and in a rural area known as the Golden Triangle, where the states of Chihuahua, Durango and Sinaloa meet. It was not clear how many troops remained in the those states.

Although marijuana typically accounts for a much greater percentage of illicit crop production, opium may be catching up in some states. Soldiers have destroyed 3,873 hectares (9,566 acres) of marijuana, and 3,324 hectares (8,210 acres) of opium poppies during the operations.

Officials did not say what accounted for the relatively high portion of opium, but local media suggested fumigation declined because the necessary aircraft was scarce.

Poppy plantations in Mexico often are well-hidden and heavily defended, making them somewhat harder to eradicate.