The United States issued a security alert for the Colombian city of Santa Marta and surrounding areas in the Magdalena and La Guajira departments.

Sept. 24 (UPI) -- The United States issued a security alert for the Colombian city of Santa Marta and surrounding areas in the Magdalena and La Guajira departments after an illegal armed group imposed a 72-hour transportation blockade, shutdown of civilian activities and curfew.

The U.S. Embassy in Colombia said the restrictions came from the Autodefensas Conquistadoras de la Sierra Nevada, or ACSN, also known as Los Pachencas, after a Colombian security operation against the organization. Colombian authorities deployed additional forces across the region in response.

Santa Marta, a major tourist destination on Colombia's Caribbean coast, has faced transportation disruptions, business closures and restrictions on civilian movement since the armed shutdown began.

An "armed shutdown," known in Colombia as a "paro armado," is a tactic used by illegal armed groups to forcibly restrict transportation, commerce and civilian activity. Unlike a civilian strike or peaceful protest, the restrictions are enforced through threats and violence.

The U.S. Embassy said authorities had reported numerous incidents, "including vehicle burnings, intimidation of commercial establishments (including armed threats and shootings), and disruption of public transportation, businesses, and movement in parts of Santa Marta and surrounding areas."

The embassy advised U.S. citizens to avoid demonstrations and areas with increased security activity, monitor local media and follow instructions from Colombian authorities.

Earlier this week, Colombian security forces carried out a major military operation that killed 13 members of the paramilitary group Autodefensas Conquistadoras de la Sierra Nevada, also known as Los Pachencas, including one of its top commanders, according to local outlets La FM and Caracol Noticias.

In response to the deaths, the armed group imposed a 72-hour transportation blockade and restrictions on civilian activity. To enforce the shutdown, Los Pachencas members opened fire on businesses and set public transportation and cargo vehicles on fire on public roads.

The Colombian government responded with a large deployment of Army troops and police units, which patrolled the streets with armored vehicles and air support as part of President Abelardo De La Espriella's new national security and urban defense strategy.

De La Espriella also led Operation Iron early Thursday, a joint military, police and judicial offensive aimed at reasserting government control over downtown Cali, Colombia's third-largest city, an area that has historically been contested by criminal organizations.

The Cali operation marked the first official deployment of the new urban security units De La Espriella pledged to create during his presidential campaign.

The Colombian government intends to use the large-scale Cali operation as a model for its security response elsewhere in the country, Semana reported.

Faced with the public security challenge posed by Los Pachencas' armed shutdown in Santa Marta, the Defense Ministry and the presidency are pursuing a similar approach: an immediate security deployment, joint Army and police patrols and judicial operations aimed at restoring government control over the affected territory.