A man who fled the US after allegedly killing his girlfriend has mysteriously escaped police custody in Kenya.

Kelvin Kangethe, 41, was arrested last week while leaving a club in Kenya's capital, Nairobi, after a months-long manhunt by Kenyan and US authorities.

A court had allowed police to hold him for 30 days awaiting his extradition.

Authorities say that after Mr Kangethe murdered his girlfriend last October, he abandoned her body in a car at Boston Logan International Airport.

He then boarded a flight to Kenya, his country of origin.

He has not commented on the allegations.

Police have shocked Kenyans by disclosing that Mr Kangethe managed to walk out of the Nairobi police station where he was being detained on Wednesday evening and boarded a public transport vehicle.

Four police officers who were on duty and a lawyer who had met Mr Kangethe before he escaped have been arrested, Nairobi police commander Adamson Bungei told local media.

The privately owned Star newspaper quoted Mr Bungei as saying that the security lapse was "embarrassing" for Kenyan police, who have since launched a new search for Mr Kangethe.

The family of Mr Kangethe's girlfriend, Margaret Mbitu, told US media that she had been planning to end their relationship before he allegedly killed her.

She was a 30-year-old Kenyan-American nurse working in Halifax, Massachusetts.

Ms Mbitu was last seen alive leaving her workplace on the evening of 30 October last year.

She was reported missing the same day and her body was discovered two days later.

Authorities believe Mr Kangethe left the US during the window between Ms Mbitu's disappearance and the discovery of her body.

They linked Mr Kangethe to the murder after security footage captured him leaving the airport parking lot where Ms Mbitu's body was later found.

He caught a flight the morning after Ms Mbitu went missing.

A Kenyan court was due to rule on Friday whether Mr Kangethe should be tried in Kenya or be extradited to face first-degree murder charges in the US, after he claimed that he had renounced his US citizenship last year.