Another police officer has been arrested over the killings of lawyer Willie Kimani, his client and two others.

Inspector General of Police Joseph Boinnet told Capital FM News that the officer, a sergeant based at the Mlolongo AP camp was arrested Monday night after being implicated in the ongoing investigations.

This brings to four the number of police officers in custody over the murders, which have shocked the nation and led to countrywide street protests by lawyers and activists.

Police have been allowed to detain the other three who were arraigned in court Monday for a fortnight to facilitate investigations before they can plead to various charges, including murder and abduction of the slain men.

The officers who appeared in court are Senior Sergeant Fredrick Leliman, Corporal Stephen Chebulet and Police Constable Silvia Wanjiku.

According to the Director of Public Prosecutions, the 14-day period will also be used to conduct a comprehensive post-mortem (which was conducted on Monday) on the three bodies so as to determine the cause of death.

The DPP contends that the detention of the three will prevent them from interfering with any witnesses in the case which has attracted a huge public outcry.

On Monday, the government called on Kenyans to be patient as investigations into the murder are conducted to uncover the truth of what happened.

Speaking after receiving a petition from 34 Civil Society Organisations, Secretary in the Internal Security office Amos Gatheca described the actions as those of rogue officers who were acting on their own initiative.

Gatheca indicated that no effort will be spared in unravelling the deaths of the three and tough action will be taken against anyone found culpable.