King Fahd, Saudi Arabia's ruler for more than 20 years, has died and his brother, Crown Prince Abdullah, 81, will take over the throne.

King Fahd died early Monday at the King Faisal Specialist Hospital in the Saudi capital of Riyadh. Saudi TV said the king was 84 years.

An official cause of death was not given. The country's information minister, Iyad bin Amin Madani, said on Saudi TV that King Fahd had "died after suffering an illness."

"With all sorrow and sadness, the royal court in the name of his highness Crown Prince Abdullah bin Abdul Aziz and all members of the family announces the death of the custodian of the two holy mosques, King Fahd bin Abdul Aziz,'' according to a statement read out by Madani.

King Fahd had been in hospital since May 27, when he was admitted with acute pneumonia. However, he had been frail since he suffered a debilitating stroke in 1995.

His brother, Crown Prince Abdullah, had acted as the de facto ruler since then.

King Fahd ruled for 23 years, taking the country through three regional wars, and more recently, a violent al Qaeda campaign to end seven decades of the royal family's rule in Saudi Arabia.

He was known as a gambler and playboy, who created close ties with America during his rule, which angered many religious extremists throughout the Arab world. It has even been rumoured that the king drank alcohol – something strictly prohibited under Islamic law.

Al Qaeda leader Osama bin Laden became enraged with Saudi Arabia over King Fahd's decision to allow U.S. forces to deploy in the country in 1990.

Bin Laden reportedly financed attacks against military bases in Saudi Arabia as retaliation for the king's actions, and King Fahd responded by ending bin Laden's Saudi citizenship in 1994.

Religious fanaticism has been a growing problem in Saudi Arabia. In December 2003, King Fahd signed an edict for theologians to gather together doctrine to off-set Islamic extremists.

He has also cracked down on imams who preach radical views.

But King Fahd had to be mindful of Saudi Arabia's conservative clerics, who formed the base of the Saudi family's support. The king funded Palestinians who fought against Israel, and also praised Islamic militants who fought against the Soviet Union in Afghanistan.

Women still have far fewer rights than men, while criminals face extreme methods of punishment -- as instructed under Sharia Islamic law – such as amputations.

News of his death pushed the price of crude oil to $61 a barrel, but the president of the oil cartel OPEC said he expected the spike to be temporary.

Analysts don't expect Crown Prince Abdullah to change Arabia's long-standing oil policy of keeping global markets well supplied to stabilize prices.

Funeral prayers will be held on Tuesday at Riyadh's Turk bin Abdullah mosque.

On Wednesday, a ceremony will confirm the succession of Crown Prince Abdullah.