MECCA, Saudi Arabia (AFP) - Saudi Arabia could earn US$8.5 billion (S$10.6 billion) from this October's hajj, according to a study published on Monday, which predicted that two million Muslims would make the pilgrimage to Mecca.

The Mecca Chamber of Commerce said revenues from the world's largest annual gathering of Muslims would increase by 3 per cent from last year.

The study was based on estimates that 1.98 million pilgrims will travel to the holy Muslim city of Mecca, including 1.38 million, or 70 per cent, from abroad.

According to the report, a pilgrim who has travelled from another country will spend an average of 17,381 riyals (S$5,790) during Hajj, which runs for five days.

A domestic worshipper pays around 4,948 riyals, the study found.

Expenses include housing, food and drink, gifts and phone bills.

Millions of people visit Islamic holy sites in Saudi Arabia for the hajj, a pilgrimage all Muslims are expected to make at least once in their lives if health and finances permit.

Saudi Arabia also hosts millions of Muslims annually for the lesser umrah pilgrimage, which may be undertaken at any time throughout the year.

Around six million Muslims took umrah during the holy fasting month of Ramadan in July this year, according to authorities.

As well as Mecca, Saudi Arabia is also home to Islam's other holiest place - Medina.