Second contingent of GSU officers responding to the first attack also ambushed.
Five security officers were killed on Tuesday in an attack by suspected Al-Shabaab terrorists on the Elwak-Kotulo road in Mandera.
The attackers also burnt a police lorry while several officers were injured in the evening ambush.
Mandera South deputy county commissioner Daniel Bundotich said three police reservists and two Administration Police officers died in the attack.
“We lost five security officers in the attack while on patrol on Elwak-Kotulo road,” he said.
A second contingent of GSU personnel that was responding to the first attack was also ambushed, Mr Bundotich added.
Nation established that the lorry that was burnt was the one the GSU officers were in.
The terrorists are said to have attacked the first security group of APs, police reservists and regular police officers as they patrolled the notorious Elwak-Kotulo stretch.
“Combined forces were on patrol before being ambushed by suspected Al-Shabaab militants at Dubacity around midday. A team responding to the attack was also attacked and their lorry burnt,’’ said Mr Bundotich. He added that another team was being assembled to respond to the two attacks.
In November, two police vehicles were burnt to ashes in the same area, compelling police to stop escorting buses.
Buses on the Mandera-Nairobi route have since switched to Marsabit-Moyale road, which is considered safer.
According to Mr Bundotich, a gun fight ensued before the suspected militants retreated.
“We are sure of more casualties on their side, considering the ground evidence,” he said
On Sunday, KDF killed five suspected Al-Shabaab terrorists believed to have been involved in an attack on Ijara Police Station in Garissa.
KDF spokesman David Obonyo said a vehicle that had been taken away by the terrorists during the attack on the police station was destroyed after explosives it was carrying exploded during a gun fight that ensued between the soldiers and the militants.