Hundreds of thousands of Muslims from around the world have started gathering in the Saudi Arabian city of Mecca ahead of the annual Hajj pilgrimage.

Nearly two million people from around 150 countries are expected to take part in the five-day pilgrimage, which starts on Saturday and is one of the five pillars of Islam, recreating the journey taken by the Prophet Mohammed in AD632.

It is the world's biggest annual gathering of people and all Muslims are expected to do Hajj at least once in their lifetime providing they are well enough and can afford to do it.

Muslim pilgrims from all around the world circling around the Kaaba at the Grand Mosque, in the Saudi city of Mecca (AFP)

Muslim pilgrims make their way at the Grand Mosque in the Muslim holy city of Mecca, Saudi Arabia (AP)

Muslim pilgrims from all around the world circling around the Kaaba at the Grand Mosque, in the Saudi city of Mecca (AFP)

Pictures show thousands of white-robed Muslims arriving in Mecca on Friday to prepare for the pilgrimage and some have begun to circle the holy Kaaba at the Grand Mosque.

Social media users have also begun to document their travels.

This year's pilgrimage has introduced new security measures to prevent a recurrence of Hajj 2015's deadly stampede, which, according to the Saudi Arabian officials, killed at least 760 pilgrims, however the actual death toll could be as high as 2,180.

More than 930 people were also injured in the incident, which was the deadliest for 25 years.

Access to the Kaaba has been suspended during prayers and officers in red berets and camouflage uniforms have surrounded crowd-controlling barricades, as part of several safety measures implemented this year after the stampede.

Muslim pilgrims make their way at the Grand Mosque in the Muslim holy city of Mecca, Saudi Arabia (AP)

General view of Muslim pilgrims from all around the world circling around the Kaaba at the Grand Mosque, in the Saudi city of Mecca (AFP)

Muslim pilgrims prepare them selves for Friday prayer in front of the Kaaba (AP)

The Kingdom has also issued pilgrims with identification bracelets, which carry a bar code readable by smartphones and that hold data such as the pilgrim's identity, nationality and where they are staying in Mecca, AFP reports.

Tens of thousands of Iranian pilgrims are absent from this year's Hajj as tensions between Saudi Arabia and Iran flare over last year's stampede, which killed more than 400 Iranians according to Tehran - the largest number of deaths reported by any country.

Thousands of Iranians marched through the streets of Tehran on Friday to protest Saudi Arabia ahead of the Hajj.