Saudi King Abdullah bin Abdulaziz died overnight Thursday in hospital, state TV reported.
Before the announcement, reported the BBC, Saudi television cut to Koranic verses, which often signifies the death of a senior royal.
King Abdullah, who was said to be aged about 90, had been in hospital for several weeks suffering from a lung infection.
The king came to the throne in 2005 but had suffered frequent bouts of ill health in recent years, including being declared "clinically dead" in 2012 .
In the context of the kingdom's conservative circles, noted CNN, King Abdullah was seen as a reformer and often came up against more hard-line clerics.
King Salman has called on the family's Allegiance Council to pay allegiance to Muqrin as his crown prince and heir, according to Reuters.