Kenyan police officers posing as hitmen for hire on New Year's Eve arrested a Rwandan woman and her brother over a murder-for-hire plot targeting a Swiss man.

The woman, whose name is yet to be revealed, is currently in custody at the Central Police Station in Nairobi, along with her brother ahead of their arraignment in court on Tuesday.

According to the detectives, the police got a tip about the chilling plot through an informer. They then launched a daring operation to meet the woman, masquerading as hitmen.

The 50-year-old Swiss target arrived in Nairobi on Boxing Day and checked into a hotel in Westlands, a neighbourhood in Nairobi. He was to leave the hotel and join the woman at an apartment in the same area.

"The team met the lady on December 30 and were informed by the said lady that the foreigner has in his possession 850,000 euros (approximately Rwf 1,185,861,477). She informed them that before the foreigner is killed, he must transfer all the money to her account," states part of the police report.

Following discussions, the officers agreed with the woman regarding the plot. These terms of the plot included an equitable distribution of the funds acquired after the planned homicide.

The process entailed fabricating an identity card featuring the female undercover officer's image, for use in securing an apartment in Westlands. The location would serve as the venue where the suspect would lure the target for dinner before executing the attack. The card was created under the alias Sarah Nafula Masika.

On the morning of Sunday, the female undercover officer, accompanied by the suspect and her 25-year-old brother, proceeded to Westlands to secure the apartment.

"Upon inspecting the suspect and her brother, two Somali knives and acid were confiscated," the police report noted.