Saudi Arabia's King Salman has named his powerful interior minister as heir in a major reshuffle that also saw the world's longest-serving foreign minister replaced.
A royal decree removed Crown Prince Muqrin bin Abdul Aziz bin Saud as next in line to the throne and replaced him with Prince Mohammed bin Nayef, 55, who headed a crackdown on al-Qaeda in the country a decade ago.
"We have decided to respond to his highness and what he had expressed about his desire to be relieved from the position of crown prince," said a statement from the royal court, carried by the official Saudi Press Agency.
The decree named "Prince Mohammed bin Nayef as crown prince" as well as deputy prime minister and said he would continue in his position of interior minister and head of the political and security council, a coordinating body.
A separate decree on Wednesday said King Salman's son, Prince Mohammed bin Salman, who is in his early 30s, will be deputy crown prince. He retains his position of defence minister.
The new deputy crown prince has played a key role in the Saudi-led coalition's aerial campaign in Yemen to try and stop the advance of Houthi fighters, backed by Iran.
Late on Wednesday, prominent Saudi officials and scholars pledged allegiance to both Nayef and bin Salman at the Royal Palace in Riyadh.
Al Jazeera's Mohamed Vall, reporting from Jizan in the country's south, said the moves represented a major change in Saudi Arabia.
"This is the first time that a grandson of the founder of the country [King Abdulaziz], rather than a son, is appointed crown prince," our correspondent said.
Nayef narrowly escaped an attempt on his life six years ago, while he was Saudi Arabia's security chief.
Since then he has remained tough on internal security. There have been many arrests of suspected al-Qaeda and more recently ISIL members since then.
Khalil Jahshan, the executive director for the Arab Centre of Washington from Fairfax, Virginia, said that the reshuffle constitutes a "political earthquake of the greatest magnitude".
"The Saudi Arabia we knew a few hours ago is no longer," Jahshan told Al Jazeera, adding: "These are serious changes that will have repercussions not only domestically but also internationally.
"This is a very decisive answer by King Salman to the doubts that many experts have expressed since he came into power with regards to his health, his decisiveness and his control over political matters in the kingdom. And this is his unequivocal answer."
Foreign minister, Prince Saud Al Faisal, was replaced with the kingdom's Washington ambassador Adel al-Jubeir.
Faisal was first named in 1975, making him the world's longest-serving foreign minister.
Faisal "asked to be relieved from his duties due to his health conditions," said the royal decree published on the official Saudi Press Agency, adding that he was appointed as an adviser and a special envoy of King Salman, as well as a supervisor on foreign affairs.
The latest nominations, part of King's Salman second cabinet reshuffle since he acceded the throne on January 23.
King Salman, 79, came to power in January after the death of his half-brother, King Abdullah, at the age of 90.
Source: Al Jazeera And Agencies