ISLAMABAD:At least 88 people were killed when a suicide bomber detonated inside a Sufi shrine crowded with devotees in Pakistan on Thursday, the deadliest in a long line of attacks on Sufis in the country.What is Sufi Islam?For centuries Pakistan was a land of Sufism, a mystical, tolerant branch of Islam whose holy men helped spread the young religion throughout the Indian subcontinent in the 13th century.Sufis believe in saints which they say can intercede for them directly with God. They have no hierarchy or organisation, instead seeking spiritual communion through music and dance at the shrines of the saints.How popular is it?Several Muslims in Pakistan are believed to follow Sufism, though it has been in the background for decades.It is concentrated in the two most populous provinces of Punjab, whose ancient city Multan is known as the city of saints, and Sindh, with hundreds of shrines dotting the region, many that are centuries old. Visiting the shrines and offering alms to the poor – and cash to the custodians – remain very popular in Pakistan, where many believe they will help get their prayers answered.Major shrines, like the one attacked on Thursday, can see hundreds of thousands of people attend for urs, festivals symbolising the marriage of Sufis and the divine, throughout the year. Where else is it practiced?Sufism exists throughout the Muslim world, most notably in Iran, Afghanistan, Pakistan and Turkey.Perhaps the most high-profile Sufi was Rumi, one of the world’s most beloved poets, who most researchers agree was born in Afghanistan but is also claimed by Iran and lived most of his life in Turkey.Why are Sufis being targeted?Sufis believe that a saint’s descendants, or peers, inherit special access to God, which one school of thought considersheretical.In Pakistan, as retired general TalatMasood pointed out, they are soft targets; shrines often see hundreds of people made ecstatic by the drumming and hashish, with little security and at times in remote, rural areas far from medical aid.Devotees are often impoverished, and the tolerance of the shrines means more vulnerable people – women and children – are usually in attendance for the dancing and music.“When there will be mass murder and mass casualties and wounded, the impact is much greater,”Masood said, adding the tactic is ‘very difficult for the government to control, because after all you can’t monitor every place.’Who was Lal Shahbaz Qalander?Thursday’s attack took place at the shrine of Lal Shahbaz Qalandar, an ascetic 13th century Muslim saint who moved to Sindh from present-day Afghanistan, according to some researchers.He is one of the ‘four friends’ or holy men credited with helping to spread Islam through South Asia by integrating it with local traditions rather than imposing it from above.‘Qalandar’ is an honorific, while ‘Lal’ means red, though why this term has been applied to the saint is unknown. His real name was said to be Syed Mohammad UsmanMarwandi.His centuries-old shrine with its distinct golden dome is widely revered in Pakistan as a symbol of spirituality and tolerance, and hundreds of thousands of people visit each year.