Armed assailants on Thursday killed three people and injured two others in Kenya's Lamu county, a coastal region near the border with Somalia, police said.
The county is part of a large swath of territory where militant group al Shabaab carries out gun and bomb attacks to pressure Kenya into withdrawing its forces from Somalia.
A Kenyan military contingent forms part of an African Union peacekeeping force that helps defend Somalia's government against the militants.
According to a report by Lamu county police seen by Reuters, the attack took place in the early afternoon when armed men sprayed bullets into a passenger bus.
"Three men were shot at close range," the report said, adding they had died instantly, while two others were injured.
The report did not give details of the bus's route or say how many people it was carrying.
In April 2015, al Shabaab fighters stormed Garissa University in the area and sought to kill Christian students. At least 148 people were killed.
The al Qaeda-affiliated al Shabaab seeks to topple Somalia's government and establish its own rule.
Last week al Shabaab claimed responsibility for a bomb attack in Mogadishu in which at least 90 people died.