An explosion at a public park in the eastern Pakistani city of Lahore left at least 69 people dead and scores injured, officials say.
The park was crowded with families, some celebrating Easter. Many victims are said to be women and children.
According to police, it appeared to be a suicide bomb. A Pakistan Taliban faction said it carried out the attack.
Pakistani President Mamnoon Hussain has condemned the blast and the regional government has announced three days of mourning.
All the major hospitals in the area were put on an emergency footing after the blast early on Sunday evening.
One eyewitness said there was chaos, with a stampede starting and children separated from their parents in the rush to escape.
According to Lahore’s deputy commissioner, Mohammad Usman, the number of injured was 193.
Facebook has activated its feature for people in Lahore to mark themselves as safe, as news of the blast spread.
Lahore is the capital of Punjab, Pakistan’s largest and wealthiest province and the political powerbase of PM 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, whom they see as a religious hero.
Mumtaz Qadri was hanged last month for the murder of Punjab governor Salman Taseer five years ago.
Salman Taseer had defended a Christian woman jailed on blasphemy charges.