The Mexican military veteran recalls overseeing interrogations during which his men beat suspects, wrapped their faces in plastic bags to cut off their oxygen and jolted them with electric shocks.

Although the screams still haunt the retired service member long after he left the military, he remains unapologetic about using torture to find drug lords and rescue kidnapping victims.

It was the only way to break the code of silence of criminals who would otherwise refuse to speak, the 30-year veteran told AFP on condition of anonymity.

"The information obtained in those interrogations becomes intelligence," said the former official, who asked that his rank, military branch and location be omitted in order to speak freely about the torture sessions he witnessed.

The rough interrogations gave criminals "the same dose (of torture) they give" captured government forces, he said.

The stark admission comes as President Enrique Pena Nieto's government faces torture scandals against troops and police amid a decade-long drug war.

When he took office in December 2012, the authorities were investigating 287 torture cases at the federal level, according to figures from the attorney general's office obtained by Amnesty International.

In 2014, the figure soared to 2,403 investigations.

Last week, a general was sentenced to 52 years in prison for ordering the torture of a man who died and whose body was incinerated by troops.

Last month, foreign experts investigating the disappearance of 43 college students said there was evidence the authorities tortured at least 17 suspects.

And in mid-April, the defense minister issued a rare apology after a video emerged showing soldiers and police putting a plastic bag over a woman's head to cut off her oxygen as they interrogated her.

- Following orders? -

The military veteran, who was deployed in some of the country's most dangerous regions near the US border, said he was "following orders" from above to torture suspects.

The army and navy did not respond to requests for comment about his claims.

Many service members suffer from post-traumatic stress syndrome, he said.

"You think I'm going to sleep calmly for four hours while hearing the screams? Screams from torture?" he said.

Although he feels guilty "spiritually speaking," he is sure "all of them were criminals."

The torture would begin with a "punch" when a suspect claimed to know nothing, the veteran said. Then a plastic bag would be placed over the head.

"When there was no more oxygen, they had to breathe and (water) is poured in the nose," he said.

Electric shocks came next.

"You have to get them wet" first, he said, justifying his actions by saying troops and police have been "completely cut to pieces, decapitated, tortured" by criminals.

Pena Nieto's predecessor, Felipe Calderon, sent tens of thousands of troops to the streets to combat drug trafficking in 2006.

The current government has vowed to keep them deployed until the country's regions are safe again.

Soldiers, marines and police have been accused of committing various abuses in the past decade.

The United Nations special rapporteur on torture said in 2015 that torture was a "generalized" practice among Mexican security forces, something the government has vehemently rejected.

But experts dismiss the official claims.

"When you imitate a war, you get all of the negative elements," said Raul Benitez Manaut, a security expert at the National Autonomous University of Mexico.

As for the defense minister's recent apology, Gustavo Fondevila, security expert at the Economic Research and Teaching Center (CIDE) think-tank, said "that was also said by the South American dictatorships."

"They can't say that it's systematic, a protocol."

Nearly a third of federal prison inmates in Mexico claimed to have been tortured or beaten into confessing crimes, a 2012 CIDE study found.

For the military veteran, however, concerns about human rights are "the most absurd thing... Where are our rights as troops?"

- A victim's nightmare -

However, Amnesty International has found innocent people who have been tortured.

Claudia Medina accuses marines of abducting and torturing her in 2012 in a case that was documented by the UN's expert.

"For me, (the authorities) are the criminals," she told AFP. "They hide behind a uniform."

Medina, 36, was accused of illegal weapons possession, drug dealing and money laundering.

After 23 days in jail and 36 hours of torture, the shop worker was exonerated due to a lack of evidence.

She remembers hearing rap music while she was bound and her eyes covered.

Her voice breaks as she recalls the punches to her neck, kicks in the stomach, electric cables around her legs and the voice of the man who raped her.

"You think that you overcome it," she says. "But no."