Saudi Arabia’s king has appointed his son Mohammed bin Salman as crown prince – replacing his nephew, Mohammed bin Nayef, as first in line to the throne.
King Salman’s decree also means Prince Mohammed bin Salman, 31, will become deputy prime minister while continuing as defence minister.
Prince Mohammed bin Nayef, 57, has been removed from his role as head of domestic security, state media say.
He has pledged allegiance to the new crown prince, news agency SPA reports.
Saudi Arabia has typically been ruled by kings in their 70s or 80s.
Prince Mohammed bin Salman’s rapid ascent is seen by the younger generation as a sign that things are changing.
Before his latest promotion, he was responsible for leading Saudi Arabia’s war in Yemen, overseeing the kingdom’s energy policy and economic reform.
He must have already ruffled a lot of feathers in a royal family that was used to being presided over by a succession of elderly men, the BBC’s Middle East editor Jeremy Bowen reports.
His father King Salman is 81 and reportedly not in the best of health, our correspondent adds.
Prince Mohammed bin Salman could lead Saudi Arabia for decades, heralding a long period of internal stability.
However, Mohammed bin Salman is close to US President Donald Trump, and could ratchet up pressure against Iran – which would raise tensions in the region.
The founder of Saudi Arabia, King Abdulaziz (known as Ibn Saud), had dozens of sons, and there are as many as 15,000 princes and princesses in the royal family.
In 2006, a decree was passed setting up a committee responsible for electing the king and crown prince. The committee is made up of senior princes of the Al Saud royal family and is known as the Allegiance Council.
Mohammed bin Salman’s new promotion to crown prince was approved by 31 out of 34 members of the council.
Analysts say those in power tend to appoint their sons to roles that will enhance their chances of being promoted – so when monarchs and crown princes change, sons can come into and out of favour.
King Salman acceded to the throne in January 2015 after the death of his half-brother Abdullah bin Abdul Aziz.
He launched his first major cabinet reshuffle a few months later, promoting Mohammed bin Nayef to crown prince and Mohammed bin Salman, who was relatively unknown at that time, to deputy crown prince.
Experts say the second reshuffle has reduced uncertainty over the line of succession, and means the king has averted a potential power struggle between his son and his nephew.