KNCHR has demanded for IG Joseph Boinnet to take action against the Kayole police boss after he allegedly assaulted and threatened an IPOA official with a firearm.
They say Nuno's weapon should be confiscated as it "could be used with irreparable lethal consequences against citizens".
Nuno is accused of Independent Policing Oversight Authority officer Humphrey Kaunya on Monday.
Kanyua had arrived with another officer at the Kayole police station to issue the OCPD with summons to appear before IPOA on various allegations, including corruption and abuse of office.
But Nuno allegedly assaulted the IPOA official and threatened him with his firearm before detaining him.
Kaunya was freed on the same day after the intervention of DPP Keriako Tobiko.
“We have learned that the same OCPD has a record of obstructing the work of IPOA and has in the past intimidated and obstructed inspection of police premises within his jurisdiction by IPOA officers,” KNCHR vice chairman George Morara said on Thursday.
“The latest actions by the Kayole OCPD is an example of the impunity that permeates our police service as well as other security organs,” he added.
But Nuno has denied the claims against him and accused the IPOA officials of disrespect and intimidation.
He said the officers banged his table and threw the summons at him after he declined to receive it.
“I arrested one of them for misconduct. I had told them to take the summons to Nairobi County police commander because such summonses should come through his office,” Nuno said.
“I told them that they must respect the office of the OCPD even if they had no respect for me and arrested one of them for misconduct.”
Nuno also denied threatening the any of the IPOA officers with a firearm.
"I was surprised to see this matter in social and mainstream media," Nuno said.
Nairobi police commander Japheth Koome also told the Star on Thursday that Nuno has not committed any offense.
“He is a very good and hardworking disciplined officer. We have so much faith in him,” Koome said.
Morara said the National Police Service has failed to adequately address rampant corruption, high crime rate, extra-judicial killings, enforced disappearances, torture, arbitrary arrests and illegal detentions.