BJP leader Sushma Swaraj also blamed "gross intelligence failure" for the blasts while Nitish said there were no intelligence inputs about the explosions either from the Centre or from the state.
Congress leader Rashid Alvi went on to say that any probe into the blasts should also find out if any political parties were behind the blasts for personal benefits.
Expressing surprise over the "coincidence" of bomb blasts and Modi's rally, Congress's Digvijay Singh called for a thorough probe, noting that it could otherwise create a "perfect setting for Modi's launch in Bihar".
Nitish said the timing of the blasts was "very worrying".
JDU leader Sabir Ali said authorities will not spare anyone behind the incidents. "But who has benefitted from the incident, who has benefited from its timing," he asked.
Asked if BJP was allegedly behind the blasts, Ali said, "the circumstances are speaking a lot of things. We are not naming anyone before the inquiry is complete but circumstances are speaking a lot."
"The police should have taken precautions after the first blast. There were no metal detectors, frisking and other security measures at the rally. The police preparations left much to be desired," he said.
Prasad said even though they saw the first blast from the podium, they played it down to prevent any panic reaction.
Defending the security arrangements, Nitish said, "There were no intelligence inputs either from the Centre or from the state. Whatever was possible to do for this kind of a programme, the administration had done.
RJD MP Ramkirpal Yadav blamed the JD(U) government for the blast, saying it must be responsible for this "lax" in security.
