Interior Secretary Carolina Toha said she would tour the deployment sites on Monday.

Soldiers will be posted -- initially for 90 days -- to the regions of Tarapaca, Antofagasta and Arica y Parinacota, according to a government decree.

Military units will be empowered to detain anyone attempting to pass through unauthorized border crossings and turn them over to local police.

The government decree argues that migratory flows have been increasing, causing a "massive arrival of people through unauthorized passages."

The Andean town of Colchane will be a primary focus of the military effort. Mayor Javier Garcia told local radio that some 400 people pass through unauthorized crossing points each day, with the largest number arriving from crisis-wracked Venezuela.

Colchane is the most heavily trafficked spot for foreigners attempting to enter Chile.

Some arrivals have set up tents in town; others wander around looking for assistance, and dozens have died of hunger, cold or disease in recent years.

The military deployment is the latest measure Chile has taken in an effort to control the migratory flow. A year ago the government widened a 600-meter (2,000-foot) trench dug years earlier.

Criminal gangs smuggling drugs and contraband have built bridges across the trench -- which undocumented migrants have used.