The incident took place barely a week after seven people were injured when a bomb exploded inside a Bhutan-bound bus in nearby Barobhisa area in the same district Aug 18.
The explosive device was recovered Thursday from West Bengal's Jalpaiguri district.
"A police officer has been killed and two others injured while trying to defuse the explosive device," an official said.
The explosive along with timers was kept on a cycle in Chowpothi in Alipurduar sub-division early Thursday.
"We suspect the involvement of KLO (Kamtapur Liberation Organisation)," said Alipurduar sub-divisional police officer Biswachand Thakur.