They said the attack in northern Panchagarh district killed 50-year-old Jajneswar Roy and wounded two Hindu devotees at the temple premises while the assassins, presumed to be three in number, fled the scene on a motorbike.
"They (assailants) first hurled stones at the temple which prompted him (Roy) to come out to see what actually happened. The killers then pounced on him and slit his throat," a TV channel quoted a devotee in the neighbourhood as saying.
"The identity of the attackers or the motive behind the murder is not clear. Definitely we will launch an investigation and manhunt to track down the killers," he said.
Sunni-majority Bangladesh has witnessed a series of systematic attacks on religious minorities in recent months that killed nine people including two foreigners and wounded nearly 100 others.
Italian aid worker Cesare Tavella was killed by unidentified assailants in Dhaka in September and and five days later Japanese farmer Kunio Hoshi was murdered. Both attacks were claimed by Islamic State-affiliated militants.