-LRB- CNN -RRB- -- A U.N. special investigator called for the resignation of top Kenyan officials and sweeping changes in the country 's security forces to end reported widespread killings by police across the African nation . The report urged President Mwai Kibaki to publicly acknowledge his commitment to ending the killings . `` The special rapporteur concluded that police in Kenya frequently execute individuals and that a climate of impunity prevails , '' Philip Alston said in a report a recently submitted to the U.N. Human Rights Council in Geneva . `` Most troubling is the existence of police death squads operating on the orders of senior police officials and charged with eliminating suspected leaders and members of criminal organizations . '' The report calls for the resignation of Kenya 's attorney general and the immediate replacement of the police commissioner . It also says Kenyan President Mwai Kibaki should publicly acknowledge his commitment to ending unlawful killings by the police . The Kenyan government expressed its `` deep displeasure '' with the report , questioning the special investigator 's `` approach , conduct and method of work . '' `` The government expresses grave concern regarding the allegations contained in the report by the special rapporteur , '' said Alfred Mutua , a spokesman for the Kenyan government . `` His questioning of the very basis of the Kenyan state and , in particular , its institutions is totally unacceptable and impinges on Kenya 's sovereignty . '' Alston also accused government security forces of torturing and killing hundreds of men in a March 2008 crackdown on a militia in the Mt. Elgon district , in western Kenya . And he said there was compelling evidence that what he called police death squads were operating in Nairobi and Central Province with a mandate to `` exterminate '' suspected Mungiki gang members . `` These are not `` rogue '' squads , but police who are acting on the explicit orders of their superiors , '' he said . The Mungiki militia , which is loyal to Kibaki 's Kikuyu tribe , began as a religious sect , but over the years has morphed into a gang that runs protection rackets -- particularly in the slums . The U.N. investigator suggested Kibaki acknowledge the alleged police killings and commit to stop them . He also advocated creating an independent civilian police oversight body , and said the prosecutor of the International Criminal Court should investigate violence after the 2007 election . He urged the government to create a witness protection program as well . Alston , who investigates human-rights problems around the world for the United Nations , traveled to Kenya at the government 's invitation . He stayed for 10 days in mid-February while 100 interviews were conducted in the U.N. member nation . There is hope for Kenya despite his criticism , Alston said . `` While the existing situation is bad , it is far from intractable , '' the report says . `` If it so chooses , Kenya can significantly reduce the prevalence of unlawful killings . ''