A Kenyan official says Somalia's Islamic extremist insurgents al-Shabab have ambushed an army truck killing one soldier and wounding two.

Mandera County Commissioner Fredrick Shisia said Sunday the soldiers were travelling to Mandera town, in Kenya's north, from Nairobi when they were ambushed by al-Shabab fighters between Elwak and Lafey towns.

Shesia said the area of attack is close to Kenya's border with Somalia making it easy for the attackers to move back into Somalia before Kenyan military reinforcements arrived at the scene.

Kenya has experienced a wave of retaliatory attacks by al-Shabab since it sent its troop to Somalia to fight the extremists in 2011. Al-Shabab militants were responsible for attack on a university in eastern Kenya this year which killed 147 people, many of them students.