By Cyrus Ombati
The 32-seater matatu was headed for the city centre from Eastleigh when the explosive that is believed to have been inside went off.
Police said at least 30 other people were admitted to various hospitals with multiple injuries following the 5pm assault.
Nairobi head of police Benson Kibue told The Standard On Sunday the explosion caused massive damage to the matatu and five other cars that had been trailing it.
“We have casualties and it seems to have been an explosion from inside the matatu. People have been badly injured,” said Mr Kibue.
He said the death toll could rise because of the nature of injuries. Witnesses said they saw limbs strewn at the scene of the blast.
The incident attracted a huge crowd at the scene on Juja Road, a few meters from Pangani Police Station. One woman was among the three who died at the scene. Another later succumbed to injuries, bringing the number of lives lost to four.
Some of those injured were taken to Guru Nanak Hospital before being transferred to Kenyatta National Hospital.
The right side of the mini-bus was ripped off. Later in the evening, there were riots along Juja Road, with the public calling for Government action.
Mr Kibue said Al Shabaab militia could have been responsible for the attack. By the time of going to press, nobody had claimed responsibility though. The motive of the attack was not yet known either.
Mr Kibue said they suspect among the killed was the man who had the explosive matter.
“The damage was massive.”
This is the third such attack to happen in a week. The first one happened last week targeting a group of police officers near Liboi border in which eight people died. Another man died in Wajir Town on Friday night in an explosion at a market.