The deadly swoops by Peruvian cops on gangs of heavily-armed criminals on the point of perpetrating kidnappings and bank robberies looked like spectacularly effective policing — at the time.

Now, it has emerged that those urgent police raids may have been akin to death squads in disguise.

Internal investigators had been quietly probing the police's actions for months, but it wasn't until the weekend that Peruvian media finally broke the story, including the reported failure of high-ranking officers to cooperate with the investigators.

The probe has reportedly already honed in on 96 officers of various ranks linked to raids in which police allegedly executed 27 presumed gangsters. The focus is on five major operations in cities along Peru's Pacific coast, including the capital Lima, between June 2012 and June 2015.

In each case, several suspected criminals died in what police later described as a "shoot-out." The only injured cops were a handful of allegedly crooked officers said to be members of the armed gangs. In one of the higher profile raids, officers gunned down five men said to be preparing to rob a gas station in downtown Lima on June 29, 2015.

One theory is that all the raids were carried out by a single death squad called in by local police commanders to deal with each gang.

The squad allegedly used informants to learn of the criminals' plans, possibly even encouraged them, before designing a raid. In each case, it appears the police could have used the intelligence to arrest their targets, rather than kill them.

The brand new government of President Pedro Pablo Kuczynski has publicly embraced the investigation. Still in his first week on the job, Interior Minister Carlos Basombrio announced he was launching a special commission to report back on the killings within 10 days.

"If those in charge of enforcing the law violate it, we'll end up in chaos," Basombrio told Peruvian newspaper La República. "Apparently [these] criminals were killed for money or to achieve power and that is very serious."

The minister is already responsible for attempting to fulfill Kuczynski's campaign promise of a total reform of Peru's police service, widely viewed here as hopelessly corrupt and inept. In addition to resistance from within the police, he can expect to face opposition from the hard-right Popular Force party of former presidential candidate Keiko Fujimori, which has a congressional majority.

Peru's homicide rate of 9.6 killings per 100,000 residents per year, according to the United Nations, is relatively low by Latin American standards. Even so, polls show that violent crime and public safety have become top concerns for most Peruvians.