RIYADH, Saudi Arabia — Saudi Arabia’s newly enthroned King Salman moved quickly Friday to name a future successor to the crown in his oil-rich kingdom, a significant appointment that puts the kingdom’s future squarely in the hands of a new generation.

King Salman bin Abdul-Aziz Al Saud’s actions came as the Sunni-ruled kingdom mourned King Abdullah, who died early Friday at the age of 90 after nearly two decades in power.

He was buried Friday afternoon in an unmarked grave, his body shrouded in a simple beige cloth without a coffin. The austere, subdued burial was in line with Islamic tradition that all people — even kings — are equal in death before God.

A royal decree affirmed Crown Prince Muqrin, 69, as Salman’s immediate successor. After Muqrin, Salman named Interior Minister Prince Mohammed bin Nayef, 55, as deputy crown prince, making him second-in-line to the throne. Mohammed is the first grandson of Saudi Arabia’s founder, King Abdul-Aziz Al Saud, to be named as a future heir.

King Salman promised in a nationally televised speech to continue the policies of his predecessors.

“We will continue adhering to the correct policies which Saudi Arabia has followed since its establishment,” Salman said.

For more than six decades, power has passed among the sons of King Abdul-Aziz, from brother to brother, since his death in 1953. But ranks of that generation, largely in their 70s and 80s, are thinning.

The decision to name Mohammed as deputy crown prince helps alleviate uncertainty over which of Abdul-Aziz’s hundreds of grandsons would ascend to the throne. It also highlighted the Al Saud family’s ability to coalesce around thorny issues of succession to ultimately preserve the stability of their rule.

Salman on Friday also appointed his son, Prince Mohammed, as Defense Minister. The prince, in his 30s, was head of his father’s royal court when Salman was crown prince and is among his most-favored sons.

In his first speech as king, Salman also made an oblique reference to the chaos gripping the greater Middle East as the extremist Islamic State group now holds a third of both Iraq and Syria.

“The Arab and the Islamic nations are in dire need of solidarity and cohesion,” the king said.

Salman, 79, had increasingly taken on the duties of the king over the past year as his ailing predecessor and half brother, Abdullah, became more incapacitated. Abdullah officially ascended to the throne in 2005, but had been de-facto ruler for years before that.

State television aired images of the prayer ahead of his burial in Riyad’s al-Oud cemetery in an area reserved for royals. Hundreds gathered outside the cemetery, which was guarded by security officials. One billboard in the capital with Abdullah’s image said: “To God we belong and to God we shall return.”