Muslim pilgrims circle counterclockwise around Islam's holiest shrine, the Kaaba, at the Grand Mosque in the Saudi Arabian holy city of Mecca, late on Sunday. The annual hajj pilgrimage begins on Tuesday, and roughly 3 million people from around the world are expected to converge at the Kaaba, in Mina and other nearby areas for the hajj, which lasts about five days. The Kaaba contains a black stone, which is revered as holy. All able-bodied Muslims are required to perform the hajj once in their lives, as one of the five pillars of Islam. Photo: AFP

Muslim pilgrims walk on a road in the holy city of Mecca on Monday. There are about 1.6 billion Muslims, or 23 percent of the world's population, making Islam the second-largest religion, according to the Pew Research Center. Photo: CFP

Muslim pilgrims take pictures while standing amongst pigeons outside the Grand Mosque in Mecca ahead of the annual hajj pilgrimage on Monday. Photo: CFP

A Muslim Pilgrim prays outside the Grand Mosque in Mecca on Sunday. The Daily Mail reported that 100,000 security personnel have been deployed to watch over the pilgrimage and about 5,000 CCTV cameras were installed across the cities of Mecca and Medina. Medina is the second-holiest site in Islam. Photo: IC