Two suicide bombers have carried out a deadly attack on a Sufi shrine in the eastern Pakistani city of Lahore.
At least 42 people died in the blasts at the popular Data Darbar shrine late on Thursday evening, officials say.
At least 175 other people were hurt in the attack, believed to be the first to target a shrine in Lahore.
Thousands of people were visiting the shrine at the time, officials say. It holds the remains of a Persian Sufi saint, Abul Hassan Ali Hajvery.
The shrine is visited by hundreds of thousands of people each year from both Sunni and Shia traditions of Islam.
For the first time in centuries, the mosque of the shrine was closed temporarily for security reasons on Friday, although officials say it may be opened later in the day.
The impact of the two blasts ripped open the courtyard of the shrine. Rescue workers could be seen clambering over the rubble as they carried out the victims.
The first attacker struck in the underground area where visitors sleep and prepare themselves for prayer, officials said.
As people fled, a second bomber detonated his explosives in the upstairs area.
The bombers are thought to have used devices packed with ball-bearings to maximise the impact of their attack.
A volunteer security guard at the shrine described scenes of devastation.
"It was a horrible scene," said Mohammed Nasir. "There were dead bodies all around with blood and people were crying."
The attack is the biggest on a Sufi shrine in Pakistan since militant attacks began in 2001.
No group has said it carried out the attack, but correspondents say the attacks continue a growing trend among militants to target members of other sects as well as minorities.
Lahore has been hit by a series of bomb attacks, including a suicide blast at anti-terrorist offices in March, when at least 13 people died.
In May, more than 90 people were killed in a double attack on the minority Ahmadi sect in the city.
Earlier, security chiefs had been congratulating themselves after June was the first month in two years in which there had been no suicide bombings in Pakistan, the BBC's Aleem Maqbool reports from Islamabad.
They said it was proof the militant networks had been disrupted.
Last year Pakistan launched a major military offensive against militant strongholds in South Waziristan.
In December the military said they had achieved victory, but subsequent reports have suggested the militants remain active in the region.