(CNN) -- Saudi Arabia's King Fahd -- whose reign was marked by unprecedented prosperity, but whose close ties with the United States stirred the passions of Islamic militants -- has died, Saudi Arabia's information minister announced Monday.
His exact age remains uncertain -- believed to be between 82 and 84.
A source told CNN's Nic Robertson that Fahd died Sunday evening. His burial is scheduled for Tuesday at 3 p.m. (8 a.m. EDT) in Riyadh.
The former Crown Prince Abdullah, Fahd's half brother, has been named the new Saudi king and Defense Minister Prince Sultan has replaced Abdullah as crown prince.
"King Abdullah bin Abdul Aziz has chosen Prince Sultan bin Abdul Aziz as Crown prince in accordance with Article 5 of the basic system of government," a statement from the Saudi royal court said.
"Allegiance will be paid by the public to King Abdullah and Prince Sultan after the noon prayers on Wednesday."
The Saudi monarch had been in and out of the hospital in recent months, most recently suffering from pneumonia-like symptoms. Fahd yielded day-to-day control of the kingdom a decade ago after suffering a stroke, with Abdullah serving as the de facto ruler since then.
Fahd assumed the throne on June 13, 1982, becoming the fifth king of Saudi Arabia. He was the son of King Abdul Aziz Bin Abdul Rahman Al-Saud, the founder of the modern Saudi Arabia.
"I will be father to the young, brother to the elderly," he once said. "I am but one of you; whatever troubles you, troubles me; whatever pleases you, pleases me."
The Saudi monarch was held in high esteem across the Arab and Muslim worlds because of his role as the custodian of the two holy mosques -- the major shrines of Islam in Mecca and Medina.
As king, he supervised projects to facilitate the hajj for the more than 2 million pilgrims from around the world who visit each year. Under his rule, Mecca was expanded to 3.5 million square feet to accommodate 1 million worshippers; Medina has grown to nearly 1.8 million square feet to accommodate 500,000 people, according to his official biography.
He was also an ardent supporter of the mujahedeen in the 1980s in their fight against the former Soviet Union in Afghanistan -- where Saudi-born terror leader Osama bin Laden first gained a following.
But it was Fahd's decision to allow U.S. forces to be based out of Saudi Arabia during the 1991 Gulf War against Iraq that outraged Islamic fundamentalists, including bin Laden who criticized his homeland for allowing "infidels" to attack another Arab country from its soil.
The United States also used a highly secret base in the kingdom to conduct special operations from during the early days of the Iraq invasion in 2003.
Al Qaeda terrorists have launched several attacks inside the kingdom in recent years. And 15 of the 19 hijackers in the September 11, 2001, terrorist attacks on the United States were from Saudi Arabia -- a fact that did not sit well with many in Washington who have been skeptical of the kingdom.
But the Bush administration has remained staunchly behind the kingdom since 9/11, calling Riyadh a key ally in the war on terror.
"The Saudis have been very aggressive in hunting down the terrorist cells that are in Saudi Arabia and we've had a good deal of success also on the terrorist financing front," U.S. Secretary of State Condoleezza Rice said during a foreign policy speech in May 2005.
Born in 1923, Fahd attended one of the kingdom's first educational institutions during his youth, and in 1953 he became Saudi's first minister of education.
For the next two decades, he served increasingly important roles, including interior minister, deputy prime minister and crown prince. In 1977, he met with U.S. President Jimmy Carter and U.S. Secretary of State Cyrus Vance about the importance of American involvement in trying to forge a lasting settlement to the Arab-Israeli conflict.
"I believe the U.S. can play an important part in solving the problem if we take into account not only American influence worldwide, but also the strong relationship between America and Israel," he said at the time.
He continued to try to work for Mideast peace over the years, including on his first visit to the United States as king in 1985 when met with President Ronald Reagan about the need for a renewed American role in the Mideast peace process.
During Fahd's tenure, the kingdom saw an economic, agricultural and educational transformation, building on its oil wealth to become an international and regional power.
"With the blessing and grace of Almighty God and with the assistance of the faithful Saudi people, we shall continue the welfare march of construction and development and maintain the gains which are reflected by comprehensive achievements in various fields," he recently said.