Kenya has been left in shock after the killing of a senior lawyer in a drive-by shooting on a busy street in the capital Nairobi.

Mathew Kyalo Mbobu, a respected lawyer and former head of a political parties' dispute tribunal, was driving home on Tuesday evening when a gunman on a motorcycle pulled alongside his vehicle and opened fire. Witnesses reported hearing multiple gunshots.

The motive for the attack, which resembles the shocking killing of a lawmaker earlier this year, is unknown. Investigations are under way.

The Law Society of Kenya has described the killing as "abhorrent" and said the crime must be "dealt with swiftly and conclusively".

It expressed concern over threats faced by lawyers, adding that the killing had "all markings of a predetermined assassination".

"Too often, advocates have been victimised and targeted for the work that they do," LSK president Faith Odhiambo said in a statement.

The shooting happened near the Lang'ata-Magadi road junction, next to a busy shopping centre in the affluent Karen estate, about 10km (six miles) from the city centre.

A gruesome video shared online shows a car's shattered window with the bloodied, lifeless body of the lawyer slouched over the steering wheel.

The police say they are investigating the shooting and have called on the public to remain calm, while appealing to them to report any information that can help the case.

"We are determined to provide the justice that [Mr Mbobu] and his loved ones deserve," the Directorate of Criminal Investigations (DCI) said in a statement.

Senate Speaker Amason Kingi said the "cold-blooded killing" of Mr Mbobu had "left us all devastated and in deep shock".

"We expect the police to carry out speedy and thorough investigations to unearth the reason and culprits behind this heinous crime and ensure justice is served," he said.

He described Mr Mbobu, who had taught him law at university, as a "distinguished advocate, an outstanding law scholar and a dedicated public servant".

Mr Mbobu was a law lecturer at the University of Nairobi and was known for his influential legal writing and for mentoring students into successful lawyers.

He was a previous chairman of the Political Parties' Dispute Tribunal (PPDT) - a quasi-judicial body established to resolve political and electoral disputes - as well as the Business Rent Premises Tribunal (BPRT), which would have put him at the heart of resolving contentious political and commercial disputes.

The tragic circumstances of Mbobu's killing have left Kenyans shocked, with the news of his death trending online.

In April, Charles Ong'ondo Were, a member of parliament, was shot dead in similar circumstances in a busy road in the capital in a suspected assassination.

Police then said several suspects had been arrested following what appeared to be a "targeted and predetermined" assassination.

Some of the suspects have since been charged.