The report by Verdad Abierta says the Urabeños -- a remnant of right wing paramilitary groups who often refer to themselves as the Gaitanista Self-Defense Forces of Colombia -- have for several weeks been prohibiting the distribution of food and restricting movement in the municipality of Achi (see Verdad Abierta map below).

They have forced grocery stores to close and have imposed a 6 p.m. curfew, Verdad Abierta reported. The criminal group even allegedly controls the length of phone calls made by residents, and has demanded extortion payments of cash, food and other valuable items.

Verdad Abierta also said there have been reports of recent murders in the area: a motorcycle taxi driver was killed in Achi in January, and in July another driver and a local business owner were both murdered; at the beginning of August, locals found a decapitated body floating in the Cauca River.

According to Verdad Abierta, local authorities have also received reports of a trail running from Achi to the nearby municipality of Tiquisio, which the Urabeños have allegedly used to torture and murder victims from the area.

The group has also reportedly been recruiting local children, who are employed as informants, coca leaf harvesters, or guards for the mining machinery used to extract gold. Local authorities have also reported cases of sexual abuse perpetrated against girls in the area, Verdad Abierta said.

A journalist from Verdad Abierta who worked on the report told InSight Crime that the Urabeños had restricted access to food as a control mechanism "to demonstrate that they are the 'authority' in the region and that nothing moves without their permission." The journalist stated that some of the inhabitants were surviving from subsistence food crops like potatoes, yucca, and bananas, but added that because of the scarcity of food at least 3,000 people were at risk of being displaced in the Achi area.

InSight Crime Analysis

The Urabeños have been known to exert social control over areas of strategic importance to their criminal interests in the past. However, the case in Achi is notable for two reasons.

First, while there have been other reported cases of the Urabeños establishing curfews, restricting access to food -- a particularly extreme measure -- does not appear to be their typical modus operandi. 

Secondly, the Urabeños typically tighten their control over an area when they are fighting another group for contested territory.

Achi is situated in the Magdalena Medio region, a swath of fertile land along the Magdalena River that has been one of the epicenters of armed conflict in Colombia. Numerous illegal armed groups have fought for control of coca production and drug trafficking routes in the area, which has a long history of guerrilla and paramilitary occupations, and has more recently seen the incursion of narco-paramilitary groups -- including the Urabeños -- known as BACRIM (for the Spanish for "criminal bands").

But in the southern part of the Bolivar province, where Achi is located, the Urabeños reportedly have an alliance with the Revolutionary Armed Forces of Colombia (FARC). According to Verdad Abierta, the FARC oversee coca cultivation and cocaine production in the area, while the Urabeños buy the finished product for distribution and export.

One possible explanation for the current measures imposed in Achi is that the Urabeños may be tightening control over the region in response to a perceived threat from the National Liberation Army (ELN) guerrilla group.

The FARC allied itself with the ELN in the region in 2009 in response to competition from BACRIM, but broke the pact two years later when the FARC's 37th Front formed an alliance with the Urabeños to cut the ELN out of the region's drug trade.

Following the FARC's change of alliances in 2011, the Urabeños increased their level of social control in the region. The Urabeños set up checkpoints on local roads, detaining motorcycle taxi drivers and other individuals to obtain information. The group also allegedly killed three people they accused of being ELN supporters in the municipality of Montecristo, near Achi.

But while battles between the Urabeños and the ELN in May led to massive displacement in the department of Choco, there have been no recent reports of conflicts between the ELN and the Urabeños near Achi. In the end, without a clear enemy in sight, the reasons for the Urabeños' siege-like tactics in Achi are not entirely clear.

Still, the situation serves as a reminder of the group's ability to exert tight control over areas of strategic and economic importance. The Urabeños' revenue streams of drug trafficking, illegal mining and extortion depend on control of territory. Lose that territory, lose those revenue streams.  

The Urabeños' ability to exert this control stems from the organization's roots in guerrilla and paramilitary groups. The Usuga brothers Juan de Dios and Dario Antonio -- who took command of the group in 2009 -- were former members of the Maoist guerrilla group the People's Liberation Army (EPL) before they joined a paramilitary organization that would later become part of the United Self-Defense Forces of Colombia (AUC).

Sometimes, the group likes to remind residents, and the government, of this control. For example, following the death of Urabeños leader Juan de Dios Usuga in a New Year's Day raid in 2012, the group imposed a curfew and forced businesses to close for 48 hours in parts of northern Colombia, costing the city of Santa Marta alone over $5 million in economic losses.

Other illegal armed groups in Colombia, particularly the FARC and the ELN, have been known to impose similar social control measures. In July, the ELN announced a three day "armed strike" to celebrate the group's 50th anniversary, which impacted businesses and transportation in the group's stronghold near the Venezuelan border.