Initial reports indicate that the first blast went off inside a 14-seater matatu while the second explosion went off near Equity Bank, Gikomba.
According to Kenya Red Cross, more than 70 people have been injured in the late Friday afternoon blast. The casualties have been rushed to different hospitals in Nairobi.
Head of bomb disposal unit, Eliud Lagat, has confirmed that there were two explosions and his officers are combing the scene.
One of the suspects has been arrested and taken to Pangani Police Station for further interrogation.
Two other suspects escaped on foot and police have launched a major manhunt for them.