The Pakistan city of Lahore explosion took place in a large park in the south-west of the city killing at least 50 people and injured dozens, where many people had gathered late on Sunday.
Police told news reporters that it appeared to be a suicide bomb. No group has said it was behind the explosion.
There is speculation that Christian families out for the Easter weekend may have been the target of the explosion.
All the major hospitals in the area have been put on an emergency footing, local media report.
The Pakistan explosion appears to have been at the main gate to the Gulshan-e-Iqbal Park in an area where cars are usually left.
Most of the dead and injured are women and children, a senior local police officer told Reuters news agency.
One eyewitness said there was chaos, with a stampede breaking out and children separated from their parents in the rush to escape.
Another told local media of pools of blood and scattered body parts in the park,.
Lahore is the capital of Punjab, Pakistan largest and wealthiest province and the political powerbase of Prime Minister Nawaz Sharif.
Pakistan has suffered regular incidents of Taliban-related violence, sectarian strife and criminal gang activity.