At least 54 people have been killed in a massive suicide bombing targeting an election rally in northwestern Pakistan. Funerals have already been held in the country, with government officials vowing to hunt down those responsible.

People reportedly screamed for help as rescuers arrived on the scene on Sunday, said rally organiser Imran Mahir.

“A person standing next to me died. Another was injured,” Mahir told the BBC. “It was a big sound. I initially thought there was a problem with the generator or the sound system. My ears have been ringing and hurting. My head is still hurting,” he recalls.

Police reportedly told the media that 12 of those who died were under the age of 12.

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Nearly 200 people killed in explosion

The victims were attending a rally organised by the Jamiat Ulema Islam party, headed by hard-line cleric and political party leader, Maulana Fazlur Rehman. The JUI-F is part of the Pakistan Democratic Alliance political coalition.

Nearly 200 people – including children – were injured when the suicide bombing went off.

Rehman is known to be a long supporter of Afghanistan’s Taliban government. He has escaped at least two known bomb attacks in 2011 and 2014.

Rehman expressed his “deep sorrow and regret” following the attack, in a statement. “Peace be upon JUI workers,” the statement reads, according to CNN. “The federal and provincial government should provide the best treatment to the injured.”

While Rehman was not injured in the attack, given he did not attend the rally, one of the JUI-F’s party members, Maulana Ziaullah, dead in the attack.

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Political attacks are ‘rare’ in Pakistan

Critically injured attendees were airlifted to a hospital in Peshawar.

There have been no immediate claims of responsibility.

Authorities said in a statement, that the suicide bomber set off his explosive vest near the stage were several party leaders were gathered.

The statement also said that initial investigation suspect the ISIL (ISIS) group behind the attack. But investigators are still working on the case.

Pakistan has reportedly witnesses a resurgence of attack by Islamist militants since last year, when a peace deal between the Pakistan Taliban and the government broke down.

A mosque bombing in January killed over 100 people in Peshawar city. In February, more than 100 people were killed in a mosque bombing inside a high-security compound. Many media outlets note that attacks on political parties are, however, rare.

The attack on Sunday comes as parties in Pakistan prepare for a general election in October or November.