Kenyan police officers in riot gear and General Service Unit (GSU) officers look at a street being cleared after riots broke out early morning in the informal settlement of Dandora in Nairobi on March 11, 2022. AFP
The attack took place on Friday in Lamu County which lies close to the Somalia border.
Workers had been constructing a bridge on the Lamu Port, South Sudan, Ethiopia Transport Corridor (LAPSSET) when they came under attack.
"Four people were shot fatally," a police report seen by AFP said.
A motorcycle rider who was caught in the crossfire was also killed, the report said, adding that the anti-terror police unit was investigating the incident.
The attack was claimed by the Al-Shabaab Islamist militant group.
The Lamu region, which includes the popular tourist beach destination of Lamu Island, has suffered frequent attacks, often carried out with roadside bombs.
Al-Shabaab fighters have staged several raids inside Kenya in retaliation for Nairobi sending troops into Somalia in 2011 as part of an African Union force to oust the jihadists.