Nairobi - A loud blast rocked Nairobi on Monday afternoon as television pictures showed a fire raging in a badly damaged building and crowds carrying a number of wounded people away from the site.
Sirens blared as emergency service crews rushed to Nairobi's Moi Avenue, a major road running through the city's central business district, which is usually busy during the lunch time hour.
"There was a huge bang followed by people screaming and shouting," said one witness who declined to be named.
Clothing, shoes have been blown out of windows from a store hit by the blast littered the road.
It was not immediately clear what caused the explosion.
There has been a string of attacks in Nairobi and the port city of Mombasa blamed on Somali militants and their sympathisers since Kenya sent troops into Somalia in October.