Muslim pilgrims in Mecca have converged on a vast tent camp in the desert, officially opening the annual Hajj pilgrimage amid sweltering temperatures.

Ahead of their trip, pilgrims circled the cube-shaped Kaaba in the Grand Mosque, Islam’s holiest site.

More than 1.5 million pilgrims from around the world have already amassed in and around Mecca for the Hajj, and the number was still growing as more pilgrims from inside Saudi Arabia joined.

Saudi authorities expect the number of pilgrims to exceed two million this year.

This year’s Hajj comes against the backdrop of the war in the Gaza Strip between Israel and Palestinian militants, which pushed the entire Middle East to the brink of a regional war between Israel and its allies on one side and Iran-backed militant groups on the other.

Palestinians in the coastal enclave of Gaza were not able to travel to Mecca for Hajj this year because of the closure of the Rafah crossing in May when Israel extended its ground offensive to the strip’s southern city of Rafah on the border with Egypt.

Palestinian authorities said 4,200 pilgrims from the occupied West Bank arrived in Mecca for Hajj.

Saudi authorities said 1,000 more from the families of Palestinians killed or wounded in the war in Gaza also arrived to perform Hajj at the invitation of King Salman of Saudi Arabia.

The 1,000 invitees were already outside Gaza – mostly in Egypt – before the closure of the Rafah crossing.

This year’s Hajj also saw Syrian pilgrims traveling to Mecca on direct flights from Damascus for the first time in more than a decade.

The move was part of an ongoing thaw in relations between Saudi Arabia and conflict-stricken Syria.

Syrians in rebel-held areas used to cross the border into neighbouring Turkey in their exhausting trip to Mecca for Hajj.

The pilgrimage is one of the Five Pillars of Islam, and all Muslims are required to make the five-day Hajj at least once in their lives if they are physically and financially able to do it.