Four police officers were charged for their involvement in the murder of a Christian human rights lawyer, his client, and their taxi driver in Kenya.

Willie Kimani, Josephat Mwenda, and Joseph Muiruri went missing last month in Nairobi after a court hearing where Mwenda testified against a police officer.

"Today, we have four AP officers charged with murder after a three-week investigation, and that hasn't happened in the history of Kenya. This marks an important occasion for police accountability in our country," said James Kironji, director of casework for IJM Kenya.

The bodies were found stuffed in sacks in the Ol-Donyo Sabuk River on July 1.

The four police officers face three counts of murder and abduction but pleaded not guilty.

Eyewitnesses testified in the court that they had seen the lawyer and his client in a police station basement cell hours after they went missing.

After the bodies were found, the Law Society of Kenya called on lawyers to boycott the courts for one week to protest against the killings.

Over 30 Kenyan and international human rights organizations released a joint statement to raise concerns about the human rights situation in the country.

"These extrajudicial killings are a chilling reminder that the hard-won right to seek justice for human rights violations is under renewed attack," said Muthoni Wanyeki from Amnesty International.

IJM has launched a petition calling on Kenyan President Uhuru Kenyatta for removal of the police officer directly involved in the abduction and murder of the three victims.

The organization fights for the cause of falsely convicted prisoners in Kenya, and has helped release about 200 unjustly detained people since 2001.

Amos Gatheca, a senior interior ministry official said that "rogue elements within the police" who were acting outside of chain of command carried out the abductions and murders.

"We still believe there are more perpetrators involved in the deaths of our colleagues, and we ask authorities to do everything in their power to bring them to justice," Kironji said.