A series of crude bombs exploded near a rally in the city of Patna yesterday, killing at least five people, shortly before opposition leader Narendra Modi was due to speak.
At least four small bombs exploded outside the venue where tens of thousands of people were gathering to hear Hindu hardliner Modi, a popular but divisive leader, launch the opposition's campaign in eastern Bihar state for general elections.
One explosion in a public toilet at a railway station in Patna killed one person, while more than 66 others were injured in the blasts near the venue, according to police. Local police officer Manu Maharaj said: "Police have detained two suspected persons in connection with this."
Junior home minister R.P.N. Singh said 20 people were injured at the venue ground.
Modi, a polarising figure particularly among religious minorities, later took to the stage, urging Hindus and Muslims to unite to overcome poverty in Bihar, a key electoral battleground for elections due next May.
"If we want to take Bihar forward we need to unite people of all religions, caste and creed together ... we want to unite people, not divide them," he told cheering supporters in a speech that did not mention the blasts.
"Our opponents are fooling people. That's why I want to ask my poor Muslim and Hindu brothers, do you want to fight against each other or against poverty?"
Modi has been campaigning to topple the ruling Congress party since he was named last month as the Bharatiya Janata Party's prime ministerial candidate for the national elections.
The chief minister of economically successful western Gujarat state, Modi is popular with the corporate world, with many in business hoping he can revive Asia's third-largest economy if elected next year.
But he remains a divisive figure, tarred by the religious riots in Gujarat in 2002 in which as many as 2,000 people were killed, mainly Muslims, according to rights groups.
Modi was chief minister at the time and denied any wrongdoing, but one of his former ministers was jailed last year for orchestrating some of the violence.
Prime Minister Manmohan Singh condemned the blasts and appealed for calm, while the government said it had ordered anti-terrorism forces to investigate who was behind the explosions.
"The Home Ministry has decided to rush the NSG [National Security Guard] and NIA [National Investigation Agency] to Bihar to inquire about how the sequence of blasts happened," Singh said in New Delhi.
Modi later said the blasts were deeply saddening. "Condolences with families of deceased and prayers with injured. I appeal for peace and calm," he tweeted.