A lobby has faulted the government for failing to adequately investigate "a spate of organised gang attacks on Western villages" during and after the March 4, 2013 general election.
In a report 'We Were Sent to Kill You: Gang Attacks in Western Kenya and the Government's Failed Response' released on Wednesday, Human Rights Watch said the state must conduct fresh investigations into the attacks and prosecute those culpable for carrying out or supporting the attacks.
In the 33-page report, the lobby said the research conducted in Busia and Bungoma counties showed that residents were attacked by a gang of armed youth from March to July 2013.
During the attacks, 10 people were killed in nine villages and more than 150 people were injured.
The attackers are alleged to have used pangas, clubs and axes.
In May 2013, businessman Timothy Nyongesa was killed in Bungoma town prompting residents to protest and march to the Bungoma South police headquarters.
Leaflets had earlier been distributed to residents of Mashambani and Wings estates in Bungoma town saying they will be "visited at night".
Some politicians were suspected of organising the attacks.
After the attacks, Bungoma Senator Moses Wetang'ula's younger brother, Fred, was grilled by CID officers and ordered to be reporting daily to the police station while former Bumula MP Bifwoli Wakoli was also grilled.
The two were however not charged in a court.
Police sources then indicated that they were investigating the existence of Kabuchai Defence Force under the command of an individual known in underground circles only as "General".
"Police utterly failed to effectively investigate the violence in the two counties. They did not collect critical evidence, and completely ignored evidence that gangs carried out these crimes during and after the 2013 elections with support from political figures," the report reads.
It says the government should expedite reforms in the police service including bolstering its investigative capacity.
The report recommends that the government must provide the police service with adequate resources to deal with gang activity and political violence.
Human Rights Watch said they interviewed 87 people, including victims, government officials, police officers, politicians, witnesses and activists.
Their investigations found out that the attacks "appeared to have been organised" as noted in one of the incidences where the "attackers demanded money and mobile phone handsets from victims without stealing anything from them".