KSA: Saudi Arabia’s Crown Prince Mohammed bin Salman has been named the kingdom’s prime minister in a cabinet reshuffle ordered by King Salman, according to a royal decree published by the official Saudi Press Agency on Tuesday.

Prince Mohammed is already de facto ruler of the world’s largest oil exporter, and the appointment formalises his role as leader of the kingdom’s government.

The crown prince, popularly known by his initials MBS, previously served as deputy prime minister as well as defence minister. He is being replaced as defence minister by his younger brother, Khalid bin Salman, who was deputy defence minister.

The royal decree reaffirmed all the other senior ministers in their posts, including Foreign Minister Prince Faisal bin Farhan Al Saud, Finance Minister Mohammed al-Jadaan and Investment Minister Khalid al-Falih.

By appointing MBS as prime minister, a role previously – and typically – held by the king, the 86-year-old monarch continues a slow but steady transfer of power in the kingdom.

The royal decree on Tuesday did not state the reasons behind the appointment, but the state-run news agency SPA said that the king – who remains head of state – will continue to chair cabinet meetings he attends.