North Eastern regional coordinator Mohamud Saleh said on Wednesday the vehicle carrying the three police reservists and two administration police officers was attacked.
He says several other officers were injured in a second attack on security officials who responded on Tuesday evening along the Elwak-Kotulo road.
Al-Shabaab has carried out a series of attacks in Kenya since 2011, when Kenya deployed troops to neighbouring Somalia to fight the extremists.
Al-Shabaab has vowed retribution for the Kenyan troop presence in Somalia. In recent years, most of the al-Shabaab attacks have been limited to areas near the Somali border and have mainly targeted security forces.
