Saudi Arabia's King Abdullah bin Abdulaziz, born the year the first car travelled the dusty streets of Riyadh, left a modernising legacy of cautious social and economic reform.

King Abdullah, believed to have been born in 1924, ruled Saudi Arabia as king since 2006, but had run the country as de facto regent for a decade before that.

After outliving two designated heirs, his younger half-brothers Sultan and Nayef, Abdullah is succeeded by Crown Prince Salman.

The new king is to persevere with Abdullah's efforts over nearly two decades to nudge powerful conservative clerics to accept cautious changes aimed at reconciling Islamic tradition with the needs of a modern economy.

Plain-spoken and avuncular, King Abdullah was born in the court of his father, King Abdulaziz Ibn Saud, in 1924, according to the Saudi embassy in Washington.

At that time Riyadh, the Saudi capital, was a small oasis town ringed by mud-brick walls at the centre of an impoverished but rapidly growing kingdom.

By the time he became de facto regent in 1995 when his predecessor King Fahd had a stroke, he was known to foreign diplomats as devout and conservative with strong ties to the kingdom's Bedouin tribes.

That reputation was soon blown away by the then-crown prince's reformist zeal as he tried to curb the indulgent habits of his large ruling family and address the alarming problem of youth unemployment by liberalising the economy to stimulate private sector growth.

However, his response to the Arab spring - a domestic security crackdown, populist economic measures and a hawkish foreign policy - disappointed some liberal Saudis.

After the terrorist attacks on the United States on 11 September 2001, in which 15 of the 19 hijackers were Saudi, and an al-Qaeda bombing campaign against Westerners inside the kingdom, he took on the conservative clergy who had promoted an intolerant Islamist message in schools and mosques.

He vowed to ignore both conservatives calling for "stagnation and immobility" and liberals seeking a "leap into darkness and reckless adventure".

The reforms were slow and only partly successful, but they skewed the dynamic of Saudi policy towards gradual change and made King Abdullah a popular leader among an increasingly young population where 60% of Saudis are under the age of 30.

Despite these reforms, he left the kingdoms political system largely untouched, with his only major political reform involving the establishment of a council of the ruling family to make succession more orderly.             

King Abdullah was staunchly opposed to the pro-democracy protests in neighbouring countries during the Arab Spring, reflecting Saudi concerns that the fall of old allies might create opportunities for regional rival Iran and al-Qaeda.

His order to spend $110 billion on social benefits, new housing and new jobs helped to avert any significant pro-democracy unrest in Saudi Arabia.

In recent years activists who have demanded change through petitions have ended up in jail, and political parties and public demonstrations are banned.

Yet even among those Saudis who called for a "day of rage" to protest against the lack of democracy, the king appeared to remain popular.

Critics of the ruling family said that was because of his government's lavish spending during his reign, a period of historically high oil revenue.

One of his first acts as king was to rein in spending on the royal family, demanding princes start paying for phone bills and air tickets rather than treating state bodies as a personal valet service.

King Abdullah also aimed to improve the position of women in his ultra-conservative country, trying to offer them better education and employment prospects and saying they will be allowed to take part in municipal elections in 2015.

He said women would be selected as members of the next Shoura Council, the appointed body that advises the government on new laws.

Despite this, women are still barred from driving and must seek the approval of a male "guardian" to work, travel abroad, open a bank account or undergo surgery in some cases.

In recent years, the king's foreign policy was increasingly focused on efforts to contain what the Sunni monarchy sees as the rising influence of Shia Muslim power Iran across the Middle East.