A suicide bomber killed at least 70 and injured more than 300 others, mostly women and children, outside a public park in the eastern Pakistani city of Lahore on Sunday, government officials and police said, striking at the heart of Prime Minister Nawaz Sharif's political heartland of Punjab.
Taliban faction Jamaat-ul-Ahrar has claimed responsibility for the attack saying the "target were Christians."
The blast occurred in the parking area of Gulshan-e-Iqbal Park, just outside the exit gate and metres away from children's swings in a busy residential area during the Easter holiday weekend.
Pakistan, a nuclear-armed nation of 190 million people, is plagued by Taliban militants. Punjab is its biggest and wealthiest province.
Eyewitnesses said they saw body parts strewn across the parking lot once the dust had settled after the blast.
"When the blast occurred, the flames were so high they reached above the trees and I saw bodies flying in the air," said Hasan Imran, 30, a resident who had come to Gulshan-e-Iqbal Park for a walk.
Mustansar Feroz, police superintendent for the area in which the park is located, said most of the injured and dead were women and children.
Media footage showed children and women standing in pools of blood outside the park, crying and screaming and rescue officials, police and bystanders carrying injured people to ambulances and private cars.
Dozens of women and children were seen being wheeled into hospitals, covered in blood. Many of the injured were transported to hospitals on taxis and auto-rickshaws due to a shortage of ambulances. Hundreds of citizens arrived outside hospitals to donate blood.
Local television channels reported that many of the dead bodies were being kept in hospital wards as morgues were overcrowded.
"We were just here to have a nice evening and enjoy the weather," Nasreen Bibi said at the Services Hospital, crying as she waited for doctors to update her on the condition of her two-year-old injured daughter.
"May God shower his wrath upon these attackers. What kind of people target little children in a park?"
Pakistani authorities launched a hunt on Monday for militants behind the suicide bomb.
"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.
Int agencies to commence ops asap to find linkages&perpetrators of Lhr suicide attk. COAS resolved that we must bring the killers of our-2
— Gen Asim Bajwa (@AsimBajwaISPR) March 27, 2016
Soon after the attack, the Punjab government ordered all public parks to be closed and announced three days of mourning in the province. The main shopping areas were shut down and many of the city's main roads were deserted.
The army was called in to control crowds outside the park. Some distraught, sobbing relatives clashed with police and rescue officials.
In 2014, Pakistan launched an offensive against Taliban and affiliated militants in North Waziristan, seeking to deprive them of safe havens from which to launch attacks in both Pakistan and Afghanistan.
Punjab has traditionally been more peaceful than other parts of Pakistan. Sharif's opponents have accused him of tolerating militancy in return for peace in his province, a charge he strongly denies.
Last year, a bomb killed a popular Pakistani provincial minister and at least eight others when it destroyed the minister's home in Punjab.