Hundreds of thousands of Muslims began the haj pilgrimage on Saturday, heading to a tent camp outside the holy city of Mecca in an itinerary retracing the route Prophet Mohammad took 14 centuries ago.
Over two million Muslim pilgrims arrived in the holy city of Mecca this week for the haj pilgrimage amid a vast security operation to avert any militant attacks, deadly stampedes or political activities that could embarrass Saudi Arabia.
Some pilgrims walked, carrying their bags, while others took buses moving slowly through the crowds as they headed to the Mina area east of Mecca. Men were dressed in simple white robes, marking a state of ihram, or ritual purity.
The pilgrims will all have arrived by Sunday morning at Mount Arafat, about 15 km (10 miles) east of Mecca. The Eid al-Adha, or feast of the sacrifice, begins on Monday, when pilgrims begin three days of casting stones at walls in a symbolic renunciation of the devil.
The government warned pilgrims not to politicise the haj.
"Saudi Arabia is above any party or political intentions behind haj. Pilgrims should not raise any slogans other than that of Islam," Islamic Affairs Minister Saleh bin Abdul-Aziz Al al-Sheikh said in comments published in Saudi newspapers.
There have been deadly clashes between police and Iranian pilgrims in the past over political slogans. Sectarian tensions have arisen recently in the Arab world after Shi'ite Muslims came to power in Iraq, emboldening Iran and its Shi'ite allies.
Disputes between Palestinian factions Hamas and Fatah delayed and prevented some Palestinian pilgrims from arriving, adding another potential flashpoint for protest.
The Saudi government is wary of militancy. Despite an al Qaeda campaign to destabilise Saudi Arabia from 2003 to 2006, the haj has never been targeted by al Qaeda militants.
Islamist militants rampaged through the Indian financial capital of Mumbai last month, killing 171 people, focusing world attention on al Qaeda-linked groups in Pakistan.
Authorities have made renovations over the past year to ease the flow of pilgrims inside the Grand Mosque and the disaster-prone Jamarat Bridge. In January 2006, 362 people were crushed to death there, the worst haj tragedy since 1990.
An extra level has been added to the bridge so pilgrims have four platforms from which to throw stones each day, according to the rites set by the Prophet Mohammad some 1,400 years ago.
The government says it will stop Saudis and residents in the country taking part without official haj permits, another cause of overcrowding. Over 1.75 million haj visas have been granted to Muslims abroad, and at least 500,000 locals receive permits.
The haj, one of the world's biggest displays of mass religious devotion and a duty for able-bodied Muslims, has been marred in the past by fires and hotel collapses, as well clashes over demonstrations and fatal overcrowding.