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.

Analysis No group has yet said that it carried out the attack, but the finger of blame is being pointed at the Taliban. The type of target, a Muslim shrine, is unusual. There are some elements among Islamist extremists, including the Taliban, who believe that worshipping at the shrines of saints is un-Islamic, and this is one theory why this shrine was attacked. There was another sectarian attack just over a month ago in Lahore in which 80 people died, when two mosques used by Ahmadi Muslims were hit by militants. This could be a battle within a battle that the militants are having with the Pakistani state.

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.

BIG MILITANT ATTACKS 28 May 2010 - 93 people killed in attacks on two Ahmadi mosques in Lahore

19 Apr 2010 - At least 23 die in suicide bombing at market in Peshawar

1 Jan 2010 - A bomb at a volleyball match kills about 100

28 Oct 2009 - At least 120 die in car bomb attack on packed market in Peshawar

15 Oct 2009 - About 40 die in a series of gun and bomb attacks

9 Oct 2009 - At least 50 die in Peshawar suicide blast

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.