A new Saudi anti-corruption body has detained 10 princes and dozens of former ministers.
Those sacked include Prince Meteb bin Abdullah, the head of the National Guard, and Adel Fakeih, the economy minister.
Abdullah al-Sultan, commander of the Saudi navy, was replaced by Fahad al-Ghafli.
Prince Alwaleed bin Talal, a billionaire businessman who owns investment firm Kingdom Holding, was among those held.
However, Saudi broadcaster Al-Arabiya said fresh investigations had been launched into the 2009 Jeddah floods and the outbreak of the Mers virus which emerged in Saudi Arabia in 2012.
The detentions came hours after the new anti-corruption committee was formed by royal decree.
No official explanation was given for the dismissals.
The changes come just months after Saudi King Salman bin Abdulaziz Al Saud replaced his nephew Mohammed bin Nayef with his son Mohammed bin Salman as the kingdom’s crown prince.
The Era Of Mohammed bin Salman :
Mohammed bin Salman has been responsible for pushing through a number of changes both at home and abroad since he became first in line to the Saudi crown.
Ian Black of the London School of Economics said the move fit a “pattern of accelerated change” since Mohammed bin Salman became heir.
“We’ve seen since June this year, very far-reaching changes,” he said, adding: “That was when Mohammed bin Salman, the son of King Salman, was appointed crown prince.
“Since Mohammed bin Salman became the crown prince in June, we’ve seen a lot of upheaval. We’ve seen the announcement of this very ambitious Saudi plan to transform the country the Saudi economy, Vision 2030.”
The dismissal of Meteb bin Abdullah as National Guard minister came shortly after a missile attack by Yemen’s Houthi rebels on Riyadh’s King Khaled International Airport.
However, Black said the two were probably not related as the sacking came bundled with changes to other ministerial portfolios.
In recent weeks, Saudi Arabia has announced an end to its long-standing ban on letting women and drive, and Mohammed bin Salman has also promised to return the country to a “moderate” form of Islam.
Since 2015 Saudi Arabia has been at war against Houthi rebels, who control much of northern Yemen on the kingdom’s southern border.