Saudi Arabia has barred more than 269,000 people without permits for the annual Hajj pilgrimage from entering Mecca this week, authorities said, as the world's largest annual gathering of people has officially begun.

Tens of thousands of pilgrims in Saudi Arabia utilized the Metro service to travel between the holy sites during this year's annual Hajj season, the Saudi Transport Ministry said.

A Saudi government spokesperson says more than 1.5 million foreign pilgrims are in the country for this year's Hajj.