Saudi Arabia's international feuds have spilled over into the Hajj, the annual Muslim pilgrimage to Mecca.

Qatar has accused the kingdom of barring its citizens, while Canadians fear being stranded there after Saudi Arabia suspended flights to Toronto following a spat over the kingdom's human rights record.

More than two million Muslims are in Mecca for the six-day ritual starting on Sunday. The Hajj is one of the five pillars of Islam which every able-bodied Muslim with the means must fulfil once.

Qatar, which Saudi Arabia blockaded in 2017, has said more than 1,200 eligible citizens have been barred from performing the pilgrimage, something the kingdom has denied.

"There is no chance this year for Qatari citizens and residents to travel for Hajj," Abdullah al-Kaabi, who runs the state's human rights committee, told Reuters. "Registration of pilgrims from the State of Qatar remains closed."