ABU DHABI — Saudi Arabia has completed security preparations for the annual Islamic pilgrimage in Mecca.

A top priority is to prevent the infiltration of Al Qaida operatives.

Saudi officials said thousands of police and security forces have been on alert throughout the country for the estimated two million Muslim pilgrims who arrived for Id Al Adha. They said authorities have increased security and imposed measures to maintain crowd control, Middle East Newsline reported.

Saudi Interior Minister Prince Nayef Bin Abdul Aziz said the security measures also included efforts to prevent infiltration of Al Qaida operatives from Iraq. Nayef said Islamic groups could be planning terrorist attacks during the four-day Islamic festival, which began on Wednesday.

"The government of Saudi Arabia is doing its best to make this pilgrimage secure for all the guests of God," Nayef said. "Security at the pilgrimage is an issue of cooperation."

Officials said the Interior Ministry has mobilized more than 50,000 troops, 7,000 of them special forces, to secure Mecca and major cities from an insurgency attack during the pilgrimage. Authorities have established checkpoints outside the city and cars were inspected for both counterband and explosives.

The security forces have been bolstered by both air and ground platforms. Officials said they include a range of armored vehicles, attack and utility and reconnaissance systems.

About 300 people a day have been arrested for trying to enter Mecca without a permit. Many were said to have been men dressed up as women.

"We have done a good job in reducing the activities of the terrorists," Interior Ministry spokesman Brig. Gen. Mansour Al Turki said. "They still have the ability to execute terrorist acts. We're doing our best to prevent such a wave."

Officials said most of the 50,000 would be deployed in Mina, where the pilgrims would throw stones at a stone column, a ceremony that has often resulted in stampedes in which hundreds were killed. They said authorities would not permit any demonstrations at the pilgrimage.

Among the forces would be a 2,000-member anti-riot force. These officers wield assault rifles and wear ski masks and camouflage uniforms.

Officials said advanced security equipment and machinery would monitor the crowds at the pilgrimage. They said some of the equipment was being introduced for the first time in the kingdom.

Officials said Al Qaida's leadership has changed over the last few months and that a new command has taken over insurgency operations. They said the Interior Ministry would identify the new Al Qaida leadership as well as its sources of financing.