Peru's government is advancing in an investigation of alleged police death squads and says it has identified nine officers, including a general, who allegedly masterminded the disappearance of at least 20 civilians since 2012.

The much-awaited preliminary report Monday night comes on the heels of comments by new Interior Minister Carlos Basombrio that there is strong evidence police officers ran death squads in different parts of the country in order to secure promotions and other benefits.

The revelations are fueling louder calls for an overhaul of Peru's free-wielding police force, which has been dogged by allegations of corruption and involvement in organized crime under former President Ollanta Humala.

Those killed were originally presented as dangerous outlaws involved in crimes such as bank robbery and kidnapping. But Deputy Interior Minister Ruben Vargas said at a news conference that 11 of the 20 killed didn't have criminal records and accused officers of falsifying intelligence reports.

Vargas didn't name any of the officers under investigation but said one of them was decorated six times for his service.

Media led by the newspaper La Republica first published allegations this month that as many as 90 officers were alleged to have been involved. The number hasn't been disputed by the government and reports said it includes lower-ranking officers who participated in staged operations..

Basombrio has likened the killings to a smaller-scale version of the so-called "false positive" cases that shook Colombia a decade ago, in which as many as 3,000 civilians were slain by government forces and falsely presented as rebels to inflate body counts that led to promotions and bonuses.

While Peru's government may be able to fine and fire officers involved in death squads, criminal charges are also being weighed. Attorney General Pablo Sanchez, a carry-over from Humala's administration, has said he ordered an organized crime prosecutor to investigate the allegations but so far has yet to present any findings.