Assailants also hurled grenades at a police station in Mankachar, a town in the Dhubri district, near the border with Bangladesh, killing one person and injuring five others, Reuters said.
Finger of suspicion
Police said they suspect the attacks were carried out by the separatist United Liberation Front of Assam (Ulfa).
Manmohan Singh, the Indian prime minister from the ruling Congress party, was set to campaign in Assam on Tuesday.
It is the second time in a week that Guwahati has been attacked.
An explosion on March 31 killed one person and injured 13 others.
Singh said that the police had recently gained information that Ulfa was planning an attack in the area.
Monday's blasts occurred on the eve of the 30th anniversary of the emergence of Ulfa.
The group has previously carried out attacks to mark its anniversary as part of a decades-long campaign of violence.
Ulfa says it is fighting for independence for the Assamese people and is one of dozens of armed groups operating in India's northeast.
It has accused the New Delhi of neglecting the Assamese while plundering the region's natural resources.
More than 10,000 people have died in fighting during the past 10 years.