Kenya Red Cross said seven of them who sustained critical injuries were airlifted to Nairobi for specialized treatment.
“Death toll from the Malindi bus and lorry accident rises has risen to five,” the Kenya Red Cross said on its twitter handle on Sunday afternoon.
Police later said the sixth officer had died while undergoing treatment in hospital.
Police said the officers were headed to Lamu for a security operation when the accident occurred at the Watamu turn-off just near Arabuko forest at about 2 pm.
Most of the officers were admitted to the Coast Provincial General Hospital with fractures and soft tissue injuries.
Police have urged motorists to remain vigilant while using public roads, particularly this festive season to curb road carnage.
Statistics at the Traffic headquarters in Nairobi show that December is among the months that record the highest number of road accidents.
Meanwhile, an Administration Police officer was lynched by a mob in a mistaken identity incident in Kawangware, Nairobi.
The officer was stoned to death when a rowdy mob confronted him and accused him of being a thief. Efforts by fellow officers to save him were futile.
Dagoretti divisional police chief Mathew Gwiyo confirmed the incident and said the officer was not on duty at the time of the attack.
“We are investigating to establish those involved, They must be prosecuted,” Gwiyo said.
He said several suspects were being interrogated over the killing but none of them was seen to be a prime suspect.