Saudi King Abdullah on Monday upgraded the National Guard, the kingdom's parallel army seen as a pillar of the ruling royals, to a ministry to be headed by his son Prince Mitab.
The decisions were announced in a decree by King Abdullah, the state news agency SPA reported.
Sandhurst-educated Prince Mitab, who heads the force, has been appointed Minister of National Guard, the decree said.
King Abdullah had himself led the National Guard from 1962 to 2010, when he handed its command over to Mitab.
The body is formed of recruits from the tribes who have traditionally backed the rule of the Saud dynasty since it spread its rule in the Arabian Peninsula.
The National Guard is a trained army of around 200,000 men, divided into infantry units, mechanised brigades, special units, and military police.
It operates in parallel, and as a palace-directed counter balance, to the Saudi ground forces.
Its duty is mainly to support the interior ministry in preserving security, combatting terrorism, and protecting vital installations across the kingdom.
It also assists the defence ministry, if needed.