An explosion on a bus in Nairobi has killed four people and wounded 36 in the fourth attack to rock the week marking the 50th anniversary of Kenya's independence.
The string of attacks, for which no one has claimed responsibility, have left a total of 13 people dead since Tuesday.
Police said they were investigating whether the explosion was caused by a grenade or an improvised explosive device and whether the attacker was in the vehicle.
Police say the bus came from Nairobi's Eastleigh neighbourhood, home to a sizeable Somali community and known as "Little Mogadishu". The bus exploded in the nearby area of Pangani.
The Red Cross said police on Saturday night dispersed a crowd of rioters in the street where the bus exploded.
AAP reports the attack comes as Kenya celebrates 50 years of independence from Britain.
Since Kenyan troops invaded southern Somalia in October 2011 to help oust the neighbouring country's al-Qaeda-linked Shebab insurgents, it has been hit by a wave of attacks - four in just the past five days.