Grenades and gunfire were aimed at a convoy carrying Mandera county governor Ali Roba, leaving two police and a civilian dead, although Roba escaped unharmed, Mandera East deputy county commissioner Elvis Korir said.
"The governor's vehicle had passed a few minutes before the attack on the security officers escorting him," said Korir.
The ambush was claimed by Somalia's Al-Qaeda-affiliated Shebab rebels.
"A Shebab commando unit attacked a Kenyan convoy travelling from Mandera to Nairobi," said Shebab military spokesman Abdulaziz Abu Musab. He said the militants destroyed two vehicles, hijacked another and captured weapons.
"The idea was to kill the governor, and all the people with him," said the spokesman. "We are at war with Kenya and such attacks must continue."
Roba's convoy was previously ambushed in October 2014.
Mandera, in Kenya's far northeast, borders Somalia and is plagued by insecurity. The area has been the scene of a string of recent Shebab attacks.
In November, Shebab gunmen held up a bus outside Mandera town on the same stretch of road as Friday's ambush. The militants separated passengers according to religion and executed 28 non-Muslims.
Ten days later 36 non-Muslim quarry workers were also massacred.