Four years ago, I was lucky enough to visit the beautiful and historic Data Darbar shrine, close to the ancient walled city in Lahore, Pakistan. It was a sweltering night in August, but there were thousands of people, men and women and children, within its walls. It was so crowded that you could only shuffle slowly in the prevailing direction of the foot traffic. At the same time, it was remarkably serene, bathed in the light of thousands of candles. The Quran was recited constantly. It was a mystical experience.

That night, security precautions around the mosque were, at best, modest. It is not an easy place to protect, with several entrances and a constant throng of visitors. But in 2006,  Lahore  had seen little of the scourge of terrorism that was beginning to plague other parts of the country.

Not so today. Last week, this renowned Sufi shrine, which contains the tomb of the 11^th century saint, Dhata Ganj Baksh, was attacked by suicide bombers. More than 40 people were killed.

It was the latest in a series of sectarian attacks in and around Lahore, Pakistan’s cultural and educational capital. At the end of May, two mosques of the minority Ahmadi sect were attacked during Friday prayers; more than 90 people were killed. Sunni extremists regard the Ahmadi as infidels because they don’t regard Mohammed as the last prophet. In 1974, they were declared to be “non-Muslims” by the state.

These attacks add a troubling dimension to Pakistan’s political violence. The Pakistani Taliban and other associated groups may have been expelled from some areas by army action (principally by the offensive in South Waziristan last year); and they are on the defensive in other “tribal agencies” along the Afghan border.

But they appear to be resurfacing in areas more important to Pakistan’s economic welfare. The biggest city, Karachi, has seen a rising tide of targeted assassinations this year, many blamed by police on the Taliban, some carried out in daylight by gunmen on motorcycles.

No group has claim responsibility for the attack in Lahore last week, and the air is already thick with intrigue. A spokesman for the Pakistani Taliban denied the group’s involvement. Some Pakistanis accuse India of being behind the attack. For their part, Pakistani officials have accused “Punjabi Taliban” of carrying out the attack in an effort to destabilize the country.

The Sufi tradition is a mystical and more tolerant “school” within Islam, but the patience of Pakistan’s Sufi community has been sorely tried by the attack on the Data Darbar, not the first Sufi shrine in Pakistan to be targeted. Some have taken to the streets in protest. Others  are demanding the resignation of Punjab’s Law Minister, Rana Sanaullah, whom they accuse of associating with extreme Sunni groups.

The provincial government has promised a crackdown on militant groups. But it is run by an opposition party at odds with the federal government in Islamabad, whose full involvement would be required in any concerted action against the “Punjabi Taliban.”