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, according to BBC. 

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, his younger cousin.