Worshippers from more than 150 countries began gathering on Friday in the Saudi Arabia city of Mecca, one of the holiest sites in Islam, to prepare for the five-day pilgrimage which starts on Saturday, September 10. This year’s Hajj is expected to be attended by more than 1.5 million pilgrims.

Preparations for Hajj 2016 at Mecca:

• To address security concerns, nearly a thousand new surveillance cameras have been installed at Mecca’s Grand Mosque, which will monitor crowd numbers, and the Jamarat stoning (a symbolic stoning of the devil based on historic tradition) will be more tightly controlled than in previous years.
• Also for the first time, pilgrims will be given electronic bracelets storing personal and medical information that will help authorities provide care and identify people.
• Water-resistant and connected to GPS, the devices will also instruct worshippers on timings of prayers and a multilingual help desk will guide pilgrims around the various rituals.

These measures are taken as last year’s Hajj was marred by a stampede that killed more than 750 people. However, counts carried out by countries who repatriated bodies showed that more than 2,000 people may have died in the crush, according to news agencies.

The disaster deepened tensions between Riyadh and Tehran, as many of the pilgrims killed were Iranian.

Notably absent this year are Iranian pilgrims. Last year, some 64,000 Iranians took part in the hajj, but disputes with the Saudi government prompted Tehran to bar its citizens from taking part this year.

Saudi Arabia has blamed Iranian officials for the decision and suggests it was politically motivated to publicly pressure the kingdom. Iran says Saudi “incompetence” caused a crush and stampede during last year’s hajj that killed more than 460 of its citizens. On Friday, thousands of Iranians marched through the streets of Tehran and other Iranian cities to protest Saudi Arabia, chanting prayers against the kingdom’s Sunni rulers after midday prayers.

To begin the hajj, hundreds of thousands of pilgrims circle the Kaaba in Mecca’s Grand Mosque. In a sign of humility and equality before God, the pilgrims shed symbols of materialism, entering a state of “ihram.” Women forgo makeup and perfume and wear loose-fitting clothing and a head covering, while men dress in seamless, white terry cloth garments.

Since arriving in Mecca over the past several weeks, hundreds of thousands have chanted, “Labayk Allahuma Labayk,” or “Here I am, God, answering your call. Here I am.”

While following a route the Prophet Muhammad once walked, the rites of hajj are believed to ultimately trace the footsteps of the prophets Ibrahim and Ismail, or Abraham and Ishmael as they are named in the Bible.