Social justice groups based in informal settlements have expressed fears that there's a killer police officer in nearly every slum in the country.

Speaking during an engagement Forum with the Independent Policing Oversight Authority (IPOA) in Nairobi on Tuesday, Mr Wilfred Olal, the convener of Social Justice Centres Working Group, raised the alarm on the situation, citing Pangani area that hosts Mathare slums as an example.

He claimed that the infamous Pangani six officers have a private police station that acts as the base for their activities.

He mentioned an officer known by locals as Hessy wa Dandora as being notorious for using social media to profile slum youth suspected to be criminals before killing them.

"So far 30 cases involving the officer calling himself Hessy have been forwarded to IPOA. Those linked to Ahmed Rashid are more than 30. Is the Authority doing anything to address this and does it monitor the patterns of these officers?" Mr Olal asked IPOA.

The Authority confessed that it has been having challenges investigating the officer(s) who go by pseudo names including Hessy wa Ndandora, Hessy wa Kayole, Majengo amongst others.

IPOA chief executive Anne Makori said there can never be one officer operating at different stations and called on members of public with information on the real identities of the officers to forward their names to the Authority for investigations.

"The Office of the Directorate of Public Prosecutions confirmed that there is no officer registered by the name Hessy at the National Police Service Commission (NPSC). Pseudo names limit our investigations," she said.

However, IPOA said its investigations on the conduct of one Mr Ahmed Rashid have reached advanced stages.

"We are making inroads in that case. Its a very sensitive one," said IPOA's Maina Njoroge.

Other than police brutality, the working group also urged the Authority to investigate the state of police officers located in slum areas noting that at Huruma police station, there are no cells for female detainees.

"The reporting desk at Huruma police station is used as the holding cell for women detainees," said Mr Olal.