A Kenyan member of parliament has been shot dead in the streets of the capital, Nairobi, by gunmen on a motorcycle in a suspected assassination.

Police said the attackers had been trailing Charles Ong'ondo Were's vehicle before one of them got off the motorbike and shot him at close range.

"The nature of this crime appears to be both targeted and predetermined," police spokesperson Muchiri Nyaga said in a statement.

The opposition MP had complained two months ago about threats to his life, local media reported.

After the shooting on late Wednesday, his driver and bodyguard, both unhurt, managed to rush the injured MP to Nairobi Hospital, where he was pronounced dead on arrival.

The attack happened along Ngong Road near a busy roundabout, often manned by traffic police and well secured with cameras.

Shortly after the shooting, senior police commanders and detectives visited the scene and investigations are under way, police said.

President William Ruto has ordered police to conduct a thorough investigation into the attack, adding: "Those responsible must be held to account."

Fellow legislators who visited the scene on Wednesday night expressed shock and outrage at the killing and called for swift investigations and justice.

Parliament Speaker Moses Wetang'ula described the MP as a "fearless and distinguished" legislator, calling his shooting "devastating".

The motive for his killing is still not clear, but the soft-spoken legislator had publicly claimed some "hired goons" were plotting to assassinate him, attributing the plot to local politics.

In February, he expressed concern over growing violence and unrest during public events in the Kasipul constituency in western Kenya, which he represented.

"When you hear I have been killed, Kasipul will not be the same again. But I know they won't kill me because I have the Bible in my phone and another one under my pillow," was said at the time.

On Thursday, homicide detectives visited the scene with Interior Minister Kipchumba Murkomen saying that "investigations have advanced".

Were was serving his second term in parliament as a member of the Orange Democratic Movement, led by veteran politician Raila Odinga.

In his statement, Odinga condemned the killing, saying the legislator was "mercilessly and in cold blood, gunned down by an assassin".

"We have lost a gallant son of the soil!" Odinga added.

Odinga lost to President Ruto in the 2022 election and rejected the results due to alleged irregularities.

The former prime minister has since struck a political deal with Ruto, which saw some opposition members join cabinet in what is referred to as the "broad-based government", which was supported.