Three days of mourning have been declared after a bomb killed more than 70 people, including 29 children, in the Pakistani city of Lahore.
Police say the explosion happened near a playground in a crowded park that was full of families.
Taliban splinter group Jamaat-ul-Ahrar said it had carried out the suicide attack, and deliberately targeted Christians celebrating Easter Day.
There were scenes of carnage as parents searched for children amid the debris.
At least 300 people were injured, with officials saying they expected the death toll to rise.
All major hospitals in the area were put on an emergency footing after the blast, early on Sunday evening (Monday NZT).
Lahore is one of Pakistan's most liberal and wealthy cities. It is the political powerbase of Prime Minister Nawaz Sharif, and has seen relatively few terror attacks in recent years.
Jamaat-ul-Ahrar spokesman Ehsanullah Ehsan said the group wanted to send a message to Mr Sharif that they "have entered Lahore", and threatened further attacks.
Jamaat-ul-Ahrar is a breakaway group from Tehrik-e Taliban Pakistan. It has carried out several other attacks on Pakistani civilians and security forces in recent months.
Mr Sharif condemned the attack, expressing "grief and sorrow over the sad demise of innocent lives". He has postponed a planned trip to the UK.
The explosion, believed to have been carried out by one suicide bomber, hit the main gate to the Gulshan-e-Iqbal park in the early evening, a short distance from the children's playground.
Officials said the device had been packed with ball bearings.
The popular was more crowded than usual, as Lahore's minority Christians were celebrating Easter at its funfair.
One man, who gave his name as Danish, said the park had been so full when he arrived he had not been able to enter.
"We went to a canteen to have something to eat, when there was suddenly a big blast," he told Reuters.
"Everyone went panic, running to all directions. Many of them were blocked at the gate of the park. Dead bodies can be found everywhere."
Hasan Imran, 30, a local resident, told Reuters: "When the blast occurred, the flames were so high they reached above the trees and I saw bodies flying in the air."
One man told Pakistan's Geo TV station he was heading towards a fairground ride with his wife and two children when he heard a huge bang and all four of them were thrown to the floor.
Police chief Haider Ashraf said the park had been a soft target for the militants, saying that while Pakistan is "in a warlike situation" there had been no specific alert issued for the park.
Punjab chief minister Shebaz Sharif later tweeted: "Words cannot describe agony we are in to see our children's blood spilled by cowards."
He said that those who target civilians "do not deserve to be called humans" and that Pakistan would "make sure that your terror infrastructure is dismantled completely".
UN Secretary-General Ban Ki-moon called the attack "appalling", saying the perpetrators should "be brought swiftly to justice".
Pakistan has suffered regular incidents of Taliban-related violence, sectarian strife and criminal gang activity.
Protest over executed Islamist gunman
Meanwhile, police have fired tear gas at thousands of protesters who marched on Pakistan's capital, Islamabad, in support of an executed Islamist gunman.
Mumtaz Qadri was hanged last month for the murder five years ago of Punjab province governor Salman Taseer.
Mr Taseer had defended a Christian woman jailed on blasphemy charges.