NEW DELHI - India's main opposition party demanded on Monday protection for its candidate for prime minister, Narendra Modi, after a series of small blasts killed six people shortly before he addressed a packed weekend rally.
While Modi was not in the vicinity of any of the blasts in the state of Bihar on Sunday, they were a reminder of India's bloody political history, that includes the assassination of former prime minister Rajiv Gandhi at a 1991 election rally.
The Hindu nationalist Modi is seen as a target of Islamist militants who hold him responsible for riots in 2002, during his first term as chief minister of Gujarat state, in which at least 1,000 people, most of them Muslims, were killed.
Sunday's violence was a sign of heightened tensions in the early stages of a campaign that has already coincided with an uptick in communal clashes between Hindus and Muslims.
India is due to elect a new government by May 2014 in a contest pitting the political outsider Modi, favoured by business, against the ruling Congress party's Rahul Gandhi, the scion of a political dynasty stretching back more than 60 years.
Modi denies any role in the 2002 riots or bias against minority Muslims. He has gathered momentum in recent weeks and opinion polls suggest his Bharatiya Janata Party (BJP) could win enough seats to form the next government in a coalition.
He used Sunday's rally to call for unity between poor people of both faiths and pundits predicted he could enjoy a ratings boost because of sympathy after the attack.
The BJP accused the Bihar government of failing to secure the ground where tens of thousands of supporters gathered and demanded that authorities overseeing the election do more to stop attacks.
One party leader, Subramanian Swamy, said he wrote to the prime minister demanding Modi be given secret-service-style security, currently reserved for serving and former prime ministers and close relatives.
"I think he should have special protection," Swamy told Reuters. "It appears to me that the huge crowds that turn out to see Narendra Modi upset those who have much to lose from him gaining power."
Modi is already given a large security detail made up of a mixture of "Black Cat" commandos and Gujarat police.
At least six crude bombs exploded near the rally ground in Bihar's capital, Patna, after an initial blast at its railway station. Police recovered four unexploded devices inside the ground, none close to the stage where Modi spoke.
Television images showed flames shooting several meters into the air when one of the devices exploded. Despite the bloodshed, Modi spoke for about an hour after rally organizers decided cancelling the event would risk triggering a stampede.