* Saudi Arabia stakes reputation on organising annual event
* Once in a lifetime duty for every Muslim who can afford it
* Officials hail complex logistical and security plans a success
By Ahmad Elhamy
MINA, Saudi Arabia, Aug 13 (Reuters) - Millions of haj pilgrims began heading back to Mecca for final prayers on Tuesday as the world's largest annual gathering of Muslims wound down without incident despite the logistical challenges and escalating regional tensions.
Senior officials said there had been no major incidents and the logistical, security and health plans had been successful, even with some heavy rainfall.
Saudi Arabia stakes its reputation on its guardianship of Islam’s holiest sites, Mecca and Medina, and its organisation of the pilgrimage. It hopes to continue expanding attendance to help to build its tourism industry.
Pilgrims participated in a symbolic stoning of the devil, part of the haj rituals, in Jamarat before returning to Mecca, where the Grand Mosque filled with worshippers preparing to depart.
Saudi pilgrim Jasem Ali Haqawi said he was grateful to the authorities for a well-run week of rituals.
"Nobody comes to the haj without things inside him that he wants to ask from God," he said while preparing to conduct final prayers in Mecca. "The sick, the indebted ... such things only God can grant and so you ask God for whatever you want."
Nearly 2.5 million pilgrims, most of them from abroad, came for the five-day ritual this year. Attendance is a religious duty, once in a lifetime, for every able-bodied Muslim who can afford it.
More than 120,000 members of the security forces and more than 30,000 health workers were on hand this week to maintain safety and provide first aid.
A crush in 2015 killed nearly 800 pilgrims, according to Riyadh, when two large groups of pilgrims arrived at a crossroads east of Mecca. Counts by countries of repatriated bodies showed that 2,000-plus people may have died, including more than 400 Iranians.
Saudi authorities said at the time that the crush may have been caused by pilgrims failing to follow crowd control rules. King Salman ordered an investigation but the results were never announced.
Iran boycotted the haj the following year, partly in response to the crush and a diplomatic rift between the two countries.
Iranians attended this year as Riyadh and Tehran continue to struggle for regional supremacy. Tensions are particularly high after the seizure of commercial vessels and attacks on tankers near the Strait of Hormuz.
The narrow waterway separating the two countries has become the focus of a stand-off between Tehran and Washington, which has beefed up its military presence in the Gulf since May.
(Writing by Stephen Kalin Editing by David Goodman)