Nearly 2 million Muslims converged on this city holy to Islam on Saturday for the annual pilgrimage. Some of the faithful offered prayers to avert a U.S.-led war on Iraq.
The start of the five-day hajj resonated on the other side of the globe, where the United States heightened its terror alert status, saying Friday that intelligence pointed to a possible attack timed to coincide with the pilgrimage.
Saudi authorities, wary of protests against a looming invasion of Iraq to topple President Saddam Hussein, deployed thousands of police in this otherwise sleepy city.
"We have taken all necessary measures and we do not expect any disturbing events during the hajj," Maj. Moussa al-Tanbi, head of the Hajj Department in the Saudi Public Security, told The Associated Press.
"There are no less than 20,000 security personnel deployed in Mecca," al-Tanbi said.
Police manned roadblocks, checking pilgrims' papers before letting them into the city. Non-Muslims cannot enter Mecca.
More than 500,000 pilgrims from inside Saudi Arabia are expected to join in excess of 1.5 million overseas arrivals.
Tunisian President Zine El Abidine Ben Ali, Yemeni President Ali Abdullah Saleh and Kuwaiti Emir Sheik Jaber Al Ahmad Al Sabah are among the leaders performing the hajj this year.
Despite calls from Saudi authorities to put politics aside during the hajj, the U.S.-Iraqi standoff has a fair share of discussion among pilgrims.
"Nobody wants war, but we are sure it will happen," Ender Serbes, a Turkish pilgrim, told The Associated Press Television News. "This is America's oil game. I think they will wait until the hajj is over and attack."
Anti-American sentiment has been running high in the Muslim world. America's perceived support of Israel against the Palestinians and its threat of war to disarm Iraq of its alleged banned non-conventional weapons are seen by many Muslims as a campaign against their faith.
"We are praying for Iraq, and we do not support America in its war against (our) religion," said Abdullah, from Pakistan.
Iranians, who insist that protests are a cornerstone of the rituals, want the Muslims' opposition to a war in Iraq to be heard through the hajj.
"The Iraqi crisis will have its repercussions among the pilgrims who will make their views heard to the world," Abbas Ali Hosseini, a Shiite cleric in Qom, Iran, said Thursday.
Jonathan Stevenson, an anti-terrorism expert at the International Institute for Strategic Studies in London, said there were ideological and logistical reasons why the hajj could be a period of high risk for terror attacks.
"There's the chance that ... with more Muslims traveling, monitoring systems would suffer overload and therefore there would be more likelihood of somebody slipping through the cracks," he said Friday.
The pilgrimage also could draw attention to American troops in Saudi Arabia, one of the main complaints of Osama bin Laden and his supporters, Stevenson said.
The pilgrimage to Mecca, birthplace of the Prophet Muhammad and home to Islam's holiest shrine, is required once in a lifetime for all Muslims who are able-bodied and can afford the trip. There are more than 1 billion Muslims worldwide.
The rituals begin with a visit to the Grand Mosque, which all pilgrims must complete by Sunday. Pilgrims then spend the night at the tent city of Mina, pray together the next morning at the gentle incline of Mount Arafat, the climax of the hajj, then wrap up rituals by sacrificing a goat, cow or camel, and finally end with the symbolic stoning of the devil.
Deaths often accompany the hajj. In 1987, more than 400 people were killed in Mecca when security forces clashed with Iranians staging an anti-U.S. demonstration. Last year, about 35 people died in a stampede while performing the "stoning of the devil" ritual. A 1997 fire in Mina killed more than 340 pilgrims.
The most deadly hajj-related tragedy was a 1990 stampede that killed 1,426 pilgrims.