PATNA, India - India’s home ministry Monday ordered increased security at election rallies after a string of bombs killed six people before a speech by hardline opposition leader Narendra Modi.

Seven small devices activated by remote control caused panic on Sunday when they were detonated shortly before Modi, prime ministerial candidate for the Bharatiya Janata Party (BJP), took to the stage in the eastern city of Patna.

Sushma Swaraj, the party’s leader in parliament, called the attack a “gross intelligence failure”, while BJP president Rajnath Singh said extra precautions should have been taken.  “It is a case of gross under-preparedness by the state, not even the minimum was done,” BJP spokeswoman Nirmala Sitharaman told AFP.

Responding to the criticism, Home Minister Sushilkumar Shinde insisted that adequate security was provided, but his ministry later issued an advisory to India’s states asking them to tighten arrangements at rallies.“It’s a security precaution,” said home ministry spokesman K.S. Dhatwalia.

Five states are going to the polls over the next six weeks in the first test of Modi’s popularity since he was named as the BJP’s prime ministerial candidate for general elections due before May next year.

The death toll from the bombings, including people caught up in the ensuing stampede, rose to six overnight after the body of another victim was recovered.

Indian media, citing unnamed police officials, said investigators believe the blasts could have been the work of the Indian Mujahideen, a domestic Islamist network.

Police say two people have been arrested and 13 others detained for questioning, while the federal government has deployed anti-terror forces to Patna, the capital of Bihar state, to investigate.

One of those arrested, known only as Imtiaz, has “given solid evidence” during interrogation which is helping investigations, local police official Manu Maharaj told AFP.

While a favourite with India’s business community, Modi is despised by many Muslims. He was chief minister of Gujarat in 2002 when the state was engulfed by communal riots in which up to 2,000 died.

His speech marked the start of his campaign in Bihar, which will be a key battleground during the general election. Its Chief Minister Nitish Kumar broke off a 17-year alliance with the BJP because of Modi’s track record.

The Patna blasts have heightened fears that next year’s elections in the world’s biggest democracy could be hit by violence.

Rahul Gandhi, expected to lead the ruling Congress party into the polls, told supporters last week that his life could be in danger — evoking the memory of the assassination of two ancestors who served as prime minister.

Rahul’s father Rajiv was killed by Tamil suicide bombers while on the campaign trail in 1991. His grandmother Indira Gandhi was shot dead by her Sikh bodyguards in 1984 in revenge for an army assault on the Golden Temple in Amritsar

Electoral rallies can often draw crowds of hundreds of thousands in India, but security measures are rudimentary.

Screening machines are often either entirely absent, or broken. And while leaders take to the stage with bodyguards, they rarely speak behind protective glass.

The attack in Patna was not the only security embarrassment on Sunday. The chief minister of the southern state of Kerala needed hospital treatment when opposition supporters pelted him with stones.