The blast, suspected to be a handiwork of the banned United Liberation Front of Asom (ULFA), took place when police were checking vehicles near the station at GS Road. The injured include two police home guard personnel.
"The blast took place at 7:55 pm near the Paltan Bazar police station, which is next to the railway station... We have to investigate who did this, but inputs say it is ULFA," Kamrup (Metro) Deputy Commissioner Ashutosh Agnihotri told reporters on the spot.
"15 persons were injured. Of them, two are serious. All the injured have been taken to GMC Hospital," Mr Agnihotri said.
Meanwhile, Chief Minister Tarun Gogoi condemned the incident and asked the district administration to identify the culprits and take necessary action.
This is the fifth such incident in the state in the last seven days. ULFA militants normally try to create trouble during the run-up to Independence Day.
Last week, six persons were injured in a grenade blast at a busy market area in Bokolia town in Karbi Anglong district.
Suspected anti-talk ULFA faction triggered three serial grenade blasts in Lakhimpur district, injuring five persons in the high security Deputy Commissioner Court road, Jail Road and Chawlkhowa areas.
Following these, many districts tightened security and took precautionary measures. Prohibitory orders were clamped in many districts with immediate effect.
Police have already arrested four persons, including an ULFA cadre and three surrendered members of the outfit, in connection with the Lakhimpur incident. Another militant, who was given the task to carry out a blast in Dibrugarh has surrendered.
Mr Gogoi had, on Saturday, said the strength of ULFA has declined and security forces have foiled many of their attempts.
The banned organisation had observed its annual 'Martyr's Day' yesterday.
Stating that the government has alerted all districts to keep a strict vigil, Mr Gogoi accused the banned outfit of getting help from "more than one country" to destabilise peace and development in the state.