Saudi king vows 'iron fist' against radicals

The Gulf state "is determined to strike with an iron fist all those who want to harm the spirit and orientation of our youth," he said during a speech to mark Islam's Eid al-Fitr - a holiday to celebrate the end of the holy fasting month of Ramadan.

King Salman, 80, also cautioned young people against "the dangers that lie in wait, notably extremism."

More than half of the Saudi population are under 25 and several have declared allegiance to the Islamic State group.

Furthermore, documents leaked in May suggest 362 Saudi nationals travelled to join the group in combat.

A large number of them hailed from central Saudi Arabia, from areas like Riyadh and Hail; and the Western Province, where Mecca and Medina are located.

Most members - 313 - came from major cities like Dammam, Riyadh, Mecca, Jeddah and Buraydah.

One hundred fifteen said on their forms they were from Riyadh, and 75 from al-Qassim, including 60 from Buraydah alone.

The comments - reiterated by the interior minister on behalf of the king - followed three bomb attacks that struck several targets in the kingdom on Monday.

Four security guards were killed when a Pakistani suicide bomber detonated an explosive device outside the Prophet's Mosque in Medina - Islam's second holiest site.

Just moments earlier, another bomber attempting to enter a Shia mosque in the kingdom's eastern province detonated a suicide belt in the car park after being refused entry.

A third suicide bomber during the early hours wounded two policemen when he blew himself up near the United States consulate in Jeddah.

No groups have yet claimed the bombings however the Islamic State has previously claimed responsibility for attacks against Saudi security forces as well as Shias in the eastern region.