Saudi Arabia (AP) — Scores of Muslim pilgrims in Mecca, Saudi Arabia, circled the Kaaba, Islam's holiest site, on Thursday, a day before heading to Mina for the official start of the hajj.

According to Saudi officials, more than 1.5 million pilgrims had arrived here till Tuesday. More people are expected to arrive. After the pilgrimage officially begins on Friday, people living in Saudi Arabia are also expected to join the pilgrimage in large numbers.

The crowds circling the Kaaba will last until Friday, the first day of the Hajj, when pilgrims will head to Mina. They will then go to Mount Arafat. From here they will head to Muzdalifah. There, pilgrims will collect pebbles. The Hajj is one of the five pillars of Islam. All Muslims who are physically and financially capable are required to perform the Hajj at least once in their lives.