Saudi Arabia marks first day of Hajj

Millions of Muslims from around the world have flocked to the Saudi Arabian city of Mecca to mark the first day of Hajj, the largest pilgrimage in the world to the holiest site in Islam.

The sheer number of pilgrims poses tremendous logistical and security challenges.

Mohamed Vall, reporting from Mecca, takes a look at the Saudi government's security preparations for the event.