The worst-affected area is around Taru, about 80km from Mombasa. BBC correspondent said the jam has been caused by repairs to the road following heavy rains. Traffic jams are common in Kenya and are often caused by its badly maintained road network but this is said to be the worst for several years.
More than 1,500 trucks have been stuck, Willingtone Kiberenge, acting chief executive of the Kenya Transporters Association, told Reuters news agency. Some motorists have been stuck in the countryside, miles from the nearest shop, since the jam began on Tuesday evening.