MOUNT ARAFAT (AFP) - The enemies of Muslim nations are trying to spread "chaos and confusion", Saudi Arabia's top cleric told Muslims from around the world in an address during the annual haj pilgrimage.

"Oh Muslim peoples, your countries have been entrusted to you, so safeguard your security and stability, your gains, your resources and public projects," Grand Mufti Sheikh Abdul Aziz al-Sheikh said in a televised address on Friday from Nimrah Mosque at Mount Arafat in western Saudi Arabia, home to Islam's holiest sites.

Close to two million Muslims from around the world were gathered there for a day of prayer at the peak of the annual haj.

"And know that you are targeted by your enemies who want to tear your ranks, turn your hearts against each other and spread chaos and confusion and beware of their conspiracies," he said from the spot where Prophet Mohammed made his final sermon 14 centuries ago.

The mufti's comments, similar to his haj sermon last year, come in the context of widespread revulsion among the world's Muslims towards Islamic State group militants.

Since last month, Saudi Arabia and four other Arab nations have joined the United States in air strikes in Syria against the militants, who have declared a "caliphate" straddling that country and Iraq where they have committed a spate of atrocities including crucifixions and beheadings.

In August, the mufti urged Muslim youth not to be influenced by "calls for jihad ... on perverted principles."

The kingdom is seeking to deter youths from becoming Islamist insurgents after Syria's conflict attracted hundreds of Saudis.

King Abdullah decreed in February jail terms of up to 20 years for citizens who travel to fight abroad.

The mufti has said that radicalism and terrorism "have nothing to do with Islam and (their proponents) are the enemy number one of Islam".