He was killed on the way home from a police station by six men with knife, said Brigadier General Zaw Min Tun, secretary of the Military True News Information Team.
The similar attack also happened recently to a police sergeant in Kyauk Taw township, he said.
Arakan Army (AA) group attacked a police outpost in Rathedaung township at 5.30am local time on Saturday, he added.
The official said that no injury was reported from both sides in the attack.
According to the military, AA has carried out a series of attacks at police outposts in Rakhine, and the government has named it as a terrorist group.