At least 20 people were injured, six of them seriously, in two explosions in Guwahati and Tinsukia suspected to be triggered by banned United Liberation Front of Assam on Saturday.
A third bomb was recovered from Tangni Bazar in Darrang district.
A bomb, kept under a truck in Fancy Bazar in Guwahati, the main commercial hub of the northeastern region, went off at around 1.30 pm causing injuries to four persons, police said.
The impact of the explosion was not severe and caused minor injuries to a labourer, a tea stall owner and two passersby, police said adding they were released after administering first aid.
Half an hour later, ULFA militants triggered another explosion at G N B Road in Tinsukia town, injuring 16 people, six of them seriously.
The area was immediately cordoned off and the injured admitted to a hospital there, police said.
In both Guwahati and Tinsukia, eye witnesses said they heard a loud noise as soon as the bomb exploded and saw smoke billowing from the spot.
A 2.5 kg bomb was recovered from a bicycle at Tangni Bazar, under Dhula police station in Darrang district at around 11.30 am. The bomb was later defused by experts of the army and Central Reserve Police Force.
Police suspected it was the handiwork of the ULFA, which was stepping up subversive activities in the run up to its foundation day on April seven.