At least 60 people have been killed and scores injured in an explosion at a public park in the eastern Pakistani city of Lahore, officials say.
The park was crowded with families at the time and most of the victims are said to be women and children.
Police told the BBC it appeared to be a suicide bomb. A Pakistan Taliban faction said it carried out the attack.
Pakistan’s president has condemned the blast and the regional government has announced three days of mourning.
All the major hospitals in the area have been put on an emergency footing.
The explosion appears to have been at the main gate to the Gulshan-e-Iqbal park in an area where cars are usually left – and a short distance from the children’s swings.
One eyewitness said there was chaos, with a stampede breaking out and children separated from their parents in the rush to escape.
Another 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.
Hasan Imran, 30, a local resident who had gone to the park for a walk told Reuters: “When the blast occurred, the flames were so high they reached above the trees and I saw bodies flying in the air.”
A health adviser to the regional government said more than 280 people had been injured and it was feared the number of dead would rise further.
The agency also reported that the army was called in to control crowds outside the park.
Facebook has activated its feature for people in Lahore to mark themselves as safe.
Lahore is the capital of Punjab, Pakistan’s largest and wealthiest province and the political power base of Prime Minister Nawaz Sharif.
Pakistan Taliban splinter group Jamaat-ul-Ahrar told local and Western media it was behind the attack.
“We claim responsibility for the attack on Christians as they were celebrating Easter,” spokesperson Ehansullah Ehsan told Pakistan’s Express Tribune.
Pakistan has suffered regular incidents of Taliban-related violence, sectarian strife and criminal gang activity.
Meanwhile in the capital, Islamabad, police fired tear gas at thousands of protesters who marched in support of Islamist gunman Mumtaz Qadri, who they see as a religious hero.
Qadri was hanged last month for the murder of Punjab governor Salman Taseer five years ago.
Mr Taseer had defended a Christian woman jailed on blasphemy charges.