Authorities in Pakistan on Monday said raids had begun in three cities to capture the militants behind Sunday's bomb attack targeting Christians, with arrests made and ammunition recovered, as the official death toll rose to at least 70 people.
The attack on Sunday evening in a busy park in the eastern city of Lahore, the powerbase of Prime Minister Nawaz Sharif, killed mostly women and children enjoying an Easter weekend outing. Pakistan is a majority-Muslim state but has a Christian population of more than 2 million.
It was the deadliest assault in Pakistan since the December 2014 massacre of 134 schoolchildren at a military-run academy in the city of Peshawar that prompted a big government crackdown on Islamist militancy.
"We must bring the killers of our innocent brothers, sisters, and children to justice and will never allow these savage inhumans to over-run our life and liberty," military spokesman Asim Bajwa said in a post on Twitter on Sunday.
On Monday, Bajwa tweeted that intelligence agencies had carried out five operations in Lahore and the Punjab cities of Faisalabad and Multan since Sunday evening. "Ops continue with more leads coming in," he wrote, before announcing arrests and the recovery of large amounts of weapons and ammunition.
Jamaat-ul-Ahrar, a faction of the Pakistani Taliban, claimed responsibility for the attack late on Sunday, and issued a direct challenge to the government.
"The target was Christians," said Ehsanullah Ehsan, a faction spokesman. "We want to send this message to Prime Minister Nawaz Sharif that we have entered Lahore."
Lahore is the capital of Pakistan's richest province, Punjab, and is seen as the country's political and cultural heartland. The provincial government has declared a state of emergency and three days of mourning, with one day declared in the rest of the country, according to the BBC.
Lahore's markets, schools, and courts were closed on Monday as the city mourned.
Rescue services spokeswoman Deeba Shahnaz said at least 70 people were killed and about 340 were wounded, with 25 in serious condition. At least one funeral was held on Monday.
Authorities said they had recovered one leg and the head of the suicide bomber, who they said was around 23 to 25 years old. Initial reports suggest at least 20 kg of explosives were used in a suicide jacket that also contained nuts and bolts, reported the Guardian.
The group has claimed responsibility for several big attacks after it split with the main Pakistani Taliban in 2014. It declared allegiance to the Islamic State but later said it was rejoining the Pakistani Taliban insurgency.
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