RIYADH, June 21 (Xinhua) -- Saudi King Salman bin Abdulaziz Al Saud declared on Wednesday his son Prince Mohammed bin Salman as the monarchy's new Crown Prince, to replace Prince Mohammed bin Nayef, Al Arabiya local news reported.

In according to Royal order released by the Saudi Press Agency, the former Crown Prince was also relieved from his post as interior minister, while Prince Salman was appointed also as deputy prime minister and kept his previous post as defense minister.

The agency confirmed that 31 out of 34 members of Saudi Arabia's Allegiance Council chose Mohammed bin Salman as the kingdom's crown prince. No reason was stated for the sudden change.

In 2015, Saudi King appointed his nephew Prince Mohammed bin Nayef as the Crown Prince after his brother former Crown Prince Mugrin bin Abdulaziz Al Saud stepped down. Prince Mohammed bin Nayef is widely known as Saudi Arabia's counterterrorism czar.

Mugrin was appointed as the Crown Prince in January of the same year after the death of late Saudi King Abdullah bin Abdulaziz Al Saud.

At the same time, the King appointed his son Prince Mohammed bin Salman as deputy crown prince and since then the young man has been leading a major economic reforms to get the country ready for the post oil era.

King Salman has called for a public pledging of allegiance to the new Crown Prince in Mecca on Wednesday, a tradition followed by Saudi Arabia as part of Islamic regulations.

Al Arabiya released a video that shows Former Saudi Crown Prince Mohammed bin Nayef pledging allegiance to the kingdom's new Crown Prince Mohammed bin Salman.

Under the same royal decree, King Salman has also appointed Prince Abdulaziz bin Saud bin Nayef as Saudi Arabia's interior minister while Ahmed bin Mohammed al-Salem was named deputy minister of interior.