An explosion on a bus in Kenya's capital killed at least five people and wounded 29 on Sunday, a police official and the Red Cross said.
Nairobi police chief Moses Ombati said there would likely be more casualties after the explosion on a 25-seater public transportation vehicle.
"There are more casualties coming in but what I can confirm is that five people have been killed," he said, adding that 10 men and three women were among the wounded.
Kenya Red Cross said 29 people had been wounded in the blast.
Ombati could not give further details about the cause of the blast in the Eastleigh suburb of Nairobi that is sometimes referred to as "little Mogadishu," because of the number of Somali immigrants who live there.
A U.N. Security official at the scene of the explosion said the blast was caused by an improvised explosive device. Ball bearings could be seen, which likely could have wounded bystanders in the busy area, according to the official who spoke on condition of anonymity because he is not allowed to speak to the press.
Kenya has been hit by a string of grenade attacks that are blamed on sympathizers of al-Shabab, Somalia's Islamist extremist rebels who are linked to al-Qaida.
Al-Shabab has vowed to carry out attacks on Kenya because it sent troops into Somalia last year to fight the rebels, who are considered a threat to Kenya's security because they have been blamed for kidnapping foreign tourists and aid workers in Kenya.