More than 8,000 Kenyans have been executed or tortured to death since 2002 when police launched a crackdown on a banned, politically linked sect, a group of Kenyan lawyers said on Sunday.
The Oscar Foundation said it had "documented 8,040 cases of death by execution and torture perpetuated by state agents and another 4,070 cases of disappearance where victims remain unaccounted for in the period between August 2002 and August 2007."
"A pattern of `systematic and selective' violation of citizen's right occurs arbitrarily, often the youth and poor people are targeted for brutality, torture and extrajudicial executions," the foundation said in a report.
"It was noted that most of the cases of torture occurred when officers attempted to extract confessions by force while extorting bribes from the suspected adherents," the report said.
"Those who refuse to part with bribes were blindfolded and led away to the killing fields where they were summarily executed," it said.
The group claimed, "a number of unknown people were secretly buried in pit latrines in [Nairobi's] Mathare and Korogocho slums after a contingent of the dreaded crack General Service Unit -- Kenyan police paramilitary wing -- mounted a crackdown to wipe out Mungiki operatives from the slum."
But police spokesman Eric Kiraithe dismissed the report, saying: "Police cannot comment on outrageous reports authored by dubious characters."
"If the authors of the report are serious, they should give the names of the victims, places where they were killed and by whom. That way, the claims can be investigated by police and the international community now or in future," he said.
The foundation, made up of human rights lawyers also offer free legal services, offered no specific evidence in its report, called "State Repression."
Earlier this month, the state-run Kenya National Commission on Human Rights implicated the Kenyan police in the execution-style deaths of nearly 500 men in June and last month in its crackdown on the Mungiki sect.
Police also rejected claims in which police were accused of executing the victims with a single bullet in the back of the head. Some of the bodies were recovered in bushes on the outskirts of the capital and others in mortuaries.
Security forces launched a crackdown on the Mungiki sect after it was banned in March 2002 when its members were involved in deadly slum violence in the capital Nairobi that claimed dozens of lives.
Once a religious group of dreadlocked youths who embraced traditional rituals, authorities say the sect has morphed into a ruthless gang blamed for criminal activities including extortion and murder.
Since March, the gang has been accused of murdering at least 43 people -- beheading several of their victims -- mainly in Nairobi slums and central Kenya.
The wave of killings peaked in June, raising fears of widespread instability in Kenya ahead of general elections next month, but a police crackdown that killed dozens of Mungiki suspects has since curbed the violence.
At the height of the crackdown, London-based Amnesty International called for an immediate probe, saying police could be guilty of a raft of human rights violations.
The allegations come ahead of a general election in Kenya next month, when President Mwai Kibaki will seek a second and final term in office.