Mexican soldiers fought late—night gun battles with gangs who forced citizens from their cars and used the vehicles to block streets in a city across the border from Texas.

The Nuevo Laredo city government posted messages on Facebook warning citizens to stay indoors as the battles erupted at several intersections on Wednesday night. City officials on Thursday said they could not immediately confirm witness reports that several gunmen were killed.

Gangs used stolen cars and buses to block several main avenues in the city across from Laredo, Texas. Several residents called local newspapers to report thefts.

“For your security, stay in your homes until the alert has passed,” the city government wrote on Facebook.

When the violence subsided, the government urged citizens to come forward and reclaim their stolen vehicles.

Nuevo Laredo is among several northern cities under siege from a turf battle between the Gulf cartel and its former enforcers, the Zetas gang of hit men. Violence has surged along the north-eastern border with the United States since the two gangs split earlier this year.

Gangs have frequently blocked streets in the middle of the cities to thwart soldiers coming to the aid of colleagues under fire.

In the northern state of Chihuahua, a banner appeared on a bridge threatening violence against “innocents” unless the state government fires its chief of police intelligence, Fernando Ornelas, the Diario de Juarez newspaper reported on Thursday.

The banner appeared in the state capital, also called Chihuahua.

Last week, drug gangs introduced a new threat to Mexico’s drug war, detonating their first successful car bomb. The attack killed a federal police officer and two others in Ciudad Juarez, Chihuahua’s largest city.

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