"There was an IED (improvised explosive device) incident... involving a civilian truck ferrying merchandise," Joseph Kanyiri, a government administrator in the area said, adding the explosion occurred on a remote stretch of road.
"Three civilians crew members riding on the lorry suffered injuries from the explosion."
The injured were evacuated for medical attention, Kanyiri said, without providing further details.
It took place in a region where Somali Islamist group al Shabaab has previously carried out attacks in the area.
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Al Shabaab is fighting to topple Somalia's central government and establish its own rule based on its own strict interpretation of Islamic sharia law.
It has also carried out deadly attacks in Lamu county in Kenya's northeast which borders Somalia and other parts of Kenya to pressure the country to withdraw its troops from Somalia.
The Kenyan military forms part of the African Union-mandated AMISOM peacekeeping force which is helping to defend Somalia's central government.
(Reporting by Humphrey Malalo; writing by Elias Biryabarema; editing by Jason Neely)
