A police reservist died on Wednesday morning after Al Shabaab militants launched an attack in Koromey, Mandera, a third attack to be reported in the county this week.
The deceased was among three reservists who were guarding the Banyole dam which is under construction.
The other two officers sustained serious injuries during the attack.
The militants torched two tractors including an excavator that were at the site as other workers ran for their lives.
The attack comes a day after at least three police were injured when Al-Shabaab gunmen attacked their vehicle in Bambahowla area.
On Monday, the gunmen killed three people and abducted three others in Falama and Jabibar areas of the upper Northeastern region along the common border with Somalia.
Among those abducted were a truck driver and his turnboy.
The gunmen attacked a construction site on the Elwak-Falama road where the driver and his turnboy were working.
Mandera South Deputy County Commissioner Nyamboga Mounda identified the truck diver as Ali Mohamed and the turn boy as Kerow Adan Abdi.
An operation is ongoing to rescue the abducted individuals.
At least 15 people are reported to have been killed in the region in the last two weeks as the militants continue to roam the county with impunity, raising serious security concerns.