New evidence has emerged linking the embattled head of Colombia's army to the alleged cover-up of civilian killings more than a decade ago.

The documents, provided to The Associated Press by a person familiar with an ongoing investigation into the extrajudicial killings, come as Gen. Nicacio Martínez Espinel faces mounting pressure to resign over orders he gave troops this year to step up attacks in what some fear could pave the way for a return of serious human rights violations.

Colombia's military has been blamed for as many as 5,000 extrajudicial killings at the height of the country's armed conflict in the mid-2000s as troops under pressure by top commanders inflated body counts, in some cases dressing up civilians as guerrillas in exchange for extra pay and other perks.

What became known as the "false positives" scandal has cast a dark shadow over the U.S.-backed military's record of battleground victories. Fifteen years later not a single top commander has been held accountable for the slayings.

Human Rights Watch in February harshly criticized President Ivan Duque's appointment of Martínez Espinel, noting that he was second-in-command of the 10th Brigade in northeast Colombia during years for which prosecutors have opened investigations into 23 illegal killings. The rights group revealed that then Col. Martínez Espinel certified payments to an informant who led to "excellent results" in a purported combat operation in which an indigenous civilian and 13-year-old girl were killed. A court later convicted two soldiers of abducting them from their home, murdering them and putting weapons on their bodies so they appeared to be rebels.

Martínez Espinel at the time of the report said he had "no idea" if he had made the payments. "God and my subalterns know how we've acted," he said.

But new documents from Colombia's prosecutor's office show that Martínez Espinel in 2005 signed off on at least seven other questionable payments. The documents were provided to the AP by someone on the condition of anonymity because they fear retaliation.

Some of the rewards, which never exceeded $500, went to supposed informants whose names and IDs didn't match. In two cases, judicial investigators found the real beneficiary was soldier Oscar Alfonso, who would go on to be sentenced to 40 years for his role in a third, unrelated civilian killing. One hidden recipient was a former paramilitary commander sentenced to 15 years for extortion.

In another inconsistency, on two occasions Martínez Espinel vouched for information leading to fighting that the same documents show took place days later. Such was the case for a payment made on May 17, 2005 to an unnamed informant and which bears Martínez Espinel's signature. The payment refers to combat with purported guerrillas on May 20 — three days later — in which an unidentified "no name" male was reported killed possessing a grenade and pistol.

"A decade ago, soldiers across Colombia lured civilians to remote locations under false pretenses — such as with promises of work — killed them, placed weapons on their lifeless bodies, and then reported them as enemy combatants killed in action," said José Miguel Vivanco, Americas director at Human Rights Watch. "One can't help wonder if any of the cockades in their uniforms, or the promotions throughout 'successful' careers, corresponds to the murder of innocent civilians committed over a decade ago."

Martínez Espinel in a statement said he faces no criminal or disciplinary investigations. He said it was up to judicial authorities to evaluate the value of the documents bearing his signature but that during his time at the 10th Brigade he had no involvement or responsibility in combat operations, instead performing a purely administrative role.

"I always have been and will be ready to answer any questions by authorities," he said.

Vivanco said it's no surprise Martínez isn't under investigation given authorities' willingness to turn a blind eye to the responsibility of top commanders in the killing spree. While Colombian courts have convicted hundreds of low-ranking soldiers for their roles in the "false positive" murders, not a single general and only a handful of coronels have so far been convicted. Under international law, commanders can be held responsible for crimes carried out by subordinates that they knew about or should have known about.

Now there are reports that Martínez Espinel as army chief is looking to reinstate the policies that critics say led to the executions.

The New York Times reported recently that Martínez Espinel commanded troops to double the number of leftist guerrillas and criminals they kill, capture or force to surrender in combat. The new guidelines, made in writing at the start of Martínez Espinel's tenure as army chief in January, raised concerns among unnamed officers cited by the Times about the heightened risk of civilian causalities.

Opponents of Duque have called for Martínez Espinel to resign, pointing to a number of suspicious killings and cover-ups by soldiers this year coinciding with the new orders. But the conservative leader has so far stood by the commander even while attempting to contain the damage.

"Zero tolerance for those who dishonor the fatherland's uniform by committing crimes," Duque said hours after the Times report sent shockwaves through the armed forces, one of Colombia's most-respected institutions.

Meanwhile, in response to the Times article the armed forces rolled back part of the controversial policy requiring field commanders to pledge in writing to double their operational results against criminal gangs and holdout rebels who have filled the void left by a 2016 peace deal with the Revolutionary Armed Forces of Colombia, or FARC.

They left unchanged, however, orders instructing officers not to "demand perfection" from sources, saying attacks on military targets should be launched when there is a "60-70% credibility" about the veracity of information.

On Friday, Duque announced the creation of a blue-ribbon panel to evaluate all military protocols and manuals to make sure they are in accordance with the government's commitment to respecting human rights and international humanitarian law.

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