The first bomb exploded on the recently-constructed platform number 10 at the Patna junction around 10.30 a.m. ahead of the Bharatiya Janata Party's prime ministerial candidate Narendra Modi's "hunkar" rally here, police said.
The other blasts took place in and around Gandhi Maidan, where BJP's prime minister nominee Narendra Modi addressed a rally hours after the explosion.
Doctors at the Patna Medical College and Hospital, where all the injured have been admitted, confirmed the death of the five in the serial explosions.
After the incident, police have appealed to people, particularly those who have gathered here for the rally, not to touch any suspected articles and inform police about it immediately.
Meanwhile, Modi arrived amid tight security to address the rally at Gandhi Maidan here.
PM condemn blasts
Prime Minister Manmohan Singh Sunday condemned the serial blasts in Patna and called upon Chief Minister Nitish Kumar to speedily investigate and punish the perpetrators.
The prime minister spoke to Nitish Kumar on telephone and urged people to maintain calm.