Makkah: Saudi security forces have arrested suspected Al Qaida militants planning attacks during the haj pilgrimage, according to media reports and security sources.

"Security forces have foiled a plot to carry out a terror attack on holy sites outside Mecca with the aim of confounding security forces," Interior Ministry spokesman Mansour Al Turki said on Friday.

Dubai-based Al Arabiya television quoted an unnamed security official as saying the suspects aimed to cause
"security confusion" during the Haj pilgrimage.

The suspects were arrested in various cities in the kingdom, the official was quoted as saying. The report did not say how many were being held.

Al Qaida-linked militants have launched a campaign to destabilise the US-allied monarchy.

Saudi Arabia beefed up security as more than two million Muslims were performing the last rituals of the yearly pilgrimage in Makkah.

Pilgrims held a mass farewell visit to the Kaaba, an ancient stone shrine which all Muslims face during their daily prayers.

Most of the pilgrims earlier performed their third stoning of walls representing the devil and left the Mina area for nearby Makkah.

In Jamarat, the stoning of the three “pillars'' went on smoothly, compared to last year's deadly stampede in which more than 300 people were killed.

Saudi authorities have completed more than half of a massive infrastructure project worth more than $1 billion that will allow pilgrims to throw stones on three levels.