Five cocktails were blasted in Dangapara Bazar area of Natore's Sadar upazila on Monday night.
A BNP worker named Whab Mandal was detained from the scene.
The incident happened around 8:30pm, said Natore Sadar Police Station OC Nasim Ahmmed.
The matter was informed to the National Emergency Service at 999 and it was immediately communicated to the Sadar police station at 8:50pm and a team rushed to the scene.
Police recovered eight more cocktails from there.
Suspected Wahab Mandal was detained from the spot, the OC added.