ISIS, the terror group known for the brutal rule it has established across large swaths of territory it controls in Iraq and Syria, is operating a camp in northern Mexico, just a few miles from the U.S. border and El Paso, Texas, Judicial Watch said.

The conservative watchdog based its report on local police and military sources, adding that federal law-enforcement and Mexican Army officials last week conducted a joint operation during which they searched the Islamist camp.

Along with Muslim prayer rugs and documents in Arabic and Urdu, they discovered plans of Fort Bliss, El Paso's 1,700 square-mile military installation that houses the U.S. Army's 1st Armored Division, Judicial Watch detailed.

The suspected ISIS camp is located in Anapra, a poor neighborhood in Ciudad Juárez, in the Mexican state of Chihuahua. According to the watchdog, a second cell operates out of Puerto Palomas, a small town west of the city of 1.3 million; this camp "targets the New Mexico towns of Columbus and Deming for easy access to the United States."

"Coyotes" engaged in human smuggling help move suspected terrorists through the desert and across the border between Santa Teresa and Sunland Park, New Mexico, sources told Judicial Watch; they apparently work for the Juárez Cartel, which controls Anapra and makes the area "an extremely dangerous and hostile operating environment" for law enforcement.

Mexican authorities, however, challenged the report, the Washington Times noted.

"The government of Mexico dismisses and categorically denies each of the statements made today by the organization Judicial Watch on the alleged presence of ISIS's operating cells throughout the border region, the country's minister for press and public affairs, told the newspaper.

"The relevant authorities operating in the region have also confirmed the inexistence of these activities with their U.S. counterparts," he added.

Judicial Watch had warned as early as last August that ISIS cells had installed themselves on Mexican territory to plan attacks on the United States, Conexión Total recalled.