At least six crude bombs exploded in this eastern Indian city near where tens of thousands of people had gathered for a massive political rally.

The blasts went off shortly before the opposition prime ministerial cadidate arrived here in Patna to launch his election campaign.

One went off here at the railway station, where many of Narendra Modi's supporters streamed in to hear him speak.

(SOUNDBITE) (Hindi) MANU MAHARAJ, SENIOR SUPERINTENDENT OF POLICE (SSP), SAYING:

"There is a bathroom here where bomb blast took place. One person was injured in the blast and he has been admitted to the hospital. Our bomb disposal team is already investigating the site."

It was the first outbreak of violence since Modi launched his leadership run.

The challenger from the Hindu Bharatiya Janata Party wants to oust the ruling coalition in the May national elections.

But critics accuse Modi of pursuing a partisan agenda, accusing him of turning a blind eye to att