Assailants believed to belong to the outlawed Mungiki sect yesterday hacked a policeman to death and then burnt his body.
And the attackers also stopped a commuter bus, robbed the crew and passengers of money and mobile phones, then set the vehicle ablaze.
The scene of the grisly action was Nairobi's Dandora Estate where an estimated 200-strong Mungiki squad wreaked mid-morning mayhem.
The commuter bus was ferrying people from the densely-populated estate to the city centre.
The mid-morning act of terror left many people with gaping wounds caused by the crude weapons, including machetes, machetes and axes, that the attackers were wielding.
The dead police officer, according to a colleague, and three others were on patrol in the estate when the marauding youths ambushed them.
Realising that it was not possible to do battle with them, they decided to escape, but the victim was caught and hacked to death by the merciless assailants.
An eye witness said the youths descended on him, cutting him several times as he cried for mercy, but that fell on deaf ears. His head had several deep cuts.
After they had killed the policeman, the youths poured a liquid which was either paraffin or petrol on his body and set it on fire. They also took away his G-3 rifle.
By 3.00 pm yesterday, his charred remains were still lying by the roadside in Dandora Phase Four, the scene of the ghastly criminal act.
Next to the body was a machete and an axe used in the heinous murder.
After their bloodthirsty mission, the youths then moved towards Dandora Phase One which borders Kariobangi Light Industries, where they ordered a driver of a Bus Track bus registration number KAE 793T to stop.
They then ordered all passengers out and in the process robbed them of money, mobile phones and other valuables.
All the money which had been collected as fare by the conductor of the bus was also taken.
At this point the marauding youths met a few police officers who they overpowered and pushed back before reinforcements came and dispersed them.
The gang then moved through Dandora, causing havoc. They pelted any passing vehicles with stones, smashing their windows and windscreens.
Three of the youths, a witness said, were armed with pistols which they fired in the air occasionally and sometimes aimed them at passing vehicles.
Some of them donned deep blue sweaters like the ones used by police officers. For about an hour they went round the estate causing mayhem and spreading terror as they made eerie war cries.
The mid-morning attack disrupted transport to and from the estate and residents were forced to walk from the Kariobangi round-about to their houses.
Before the attack, some of the residents said, the suspected Mungiki adherents held a meeting in the neighbouring Korogocho Estate while others met at Maili Saba.
Fear gripped the area and most of the residents locked themselves inside their houses and left only when it was extremely necessary.
They could be seen peeping through their windows to have a glimpse of what was happening outside.
There was heavy police presence in the area and several suspects were rounded up and taken to Buru Buru Police Station.
An Isuzu Trooper, registration number KXW 462 suspected to have been used in the attack, was towed to the Buru Buru Police Station.
Some of the attackers were said to have been moving in Nissan vans.