Around 2.5 million Muslims begin Friday the rituals of the hajj pilgrimage, the world's largest annual assembly, leaving Saudi authorities with a daunting security and safety challenge.
Saudi authorities have mobilised some 100,000 security and civil defence personnel to insure a smooth pilgrimage and avoid deadly incidents that marred the extremely crowded rites in the past.
"We will mobilise all our means to prevent any harm against any pilgrim or any group of pilgrims," Saudi Interior Minister Prince Nayef bin Abdul Aziz, who recently became the crown prince of the Muslim kingdom said on Tuesday.
He made the remark during an inspection tour of hajj preparations as anti-riot and anti-terrorism police paraded in front of the kingdom's internal security czar as police and rescue helicopters hovered overhead.
The hajj rituals begin Friday and peak on Saturday when all pilgrims assemble in the Arafat plain outside Mecca, and end with Eid al-Adha, or the Feast of Sacrifice, which will be celebrated on Sunday.
Around 1.7 million Muslims are due to descent on Mecca from around the world while between 700,000 and 800,000 pilgrims will be coming from inside Saudi Arabia.
Coping with the world's largest annual human assembly poses a security headache for Saudi Arabia -- guardian of the two holiest Muslim shrines in the cities of Mecca and Medina, the birth places of Islam.
The oil kingpin has invested billions of dollars over the years to avoid deadly stampedes that marred the hajj in the past.
In January 2006, 364 pilgrims were killed in a stampede at the entrance to a bridge leading to the stoning site in Mina, outside Mecca, while 251 were trampled to death in 2004.
In July 1990, 1,426 pilgrims were trampled or asphyxiated to death in a stampede in a tunnel, also in Mina.
The deaths prompted authorities to dismantle the old bridge and replace it with a multi-level with one-way lanes to ensure a smooth flow of pilgrims.
Saudi Arabia also launched a new $10.6-billion project for a new extension to Mecca's Grand Mosque to increase its capacity to two million worshippers.
Investments also included a light-railway connection linking the holy sites.
The hajj this year coincides with the Arab Spring democracy protests that have swept many nations in the region and led so far to the unseating of three autocratic leaders in Tunisia, Egypt and Libya.
"My joy has no bounds," said pilgrim Adel Abu Kasseh of Libya, where former dictator Muammar Gaddafi was killed last month after an eight-month armed conflict to unseat him.
"It is the first time that I perform the pilgrimage after my country was liberated," he said.
Prince Nayef has insisted that the violence that has gripped some Arab countries in recent months is an "internal affair", but he has stressed that Saudi Arabia was ready for all situations.
"The kingdom is ready to face up to all situations, whatever they may be," he said on Tuesday.
The crown prince also dismissed any threat from pilgrims coming from Shiite Iran, despite rising tension between Tehran and Riyadh over an alleged Iranian plot to kill the Saudi envoy to Washington and past confrontations.
"The Iranians have always shown their respect for the hajj," he said.
A total of 97,000 Iranians -- the maximum allowed for Iran under a Saudi system apportioning pilgrim quotas among the world's biggest Muslim countries -- are in the holy cities of Mecca and Medina, Iranian media said Monday.
"We hope this year's hajj (pilgrimage) will take place in a very calm and spiritual atmosphere," the representative of Iran's supreme leader Ayatollah Ali Khamenei at the pilgrimage, Hojatoleslam Ali Ghazi Asgar, said last week.
Saudi security forces have several times in the past confronted Iranian pilgrims holding anti-US and anti-Israeli protests.
In 1987, Saudi police efforts to stifle such a demonstration sparked clashes in which 402 people died, including 275 Iranians.
Iran has fiercely denied US accusations that it had a hand in a thwarted plot to kill the Saudi ambassador to Washington, Adel al-Jubeir. It has emphasised its "good relations" with its Arab neighbour across the Gulf.
Saudi Arabia's top cleric, Sheikh Abdul Aziz al-Sheikh, said on Tuesday it was a "sin" to attempt to disrupt the pilgrimage "over political reasons."