There has been an outpouring of public support for Saudi Arabia’s newly minted crown prince Mohammed bin Salman in the days since he was appointed, although some has come from more unlikely corners.

The 31-year-old replaced his cousin Mohammed bin Nayef as next in line to the throne after a royal decree was issued by his father, King Salman, on Tuesday.

Advertisements and proclamations have been churned out by public figures such as clerics and royals and businessmen in their thousands in a country where dissent against the absolute monarchy is almost non-existent - but a full page advertisement taken out in a Saudi newspaper by McDonald’s, wishing the promoted prince “peace and prosperity”, has perplexed many people both inside the kingdom and internationally.

"We renew our allegiance and obedience for his royal highness, the servant of the two holy mosques, King Salman the son of Abdul Aziz Al Saud," the ad published on Wednesday read.

“And we support Amir Mohammed bin Salman, his son, to become Minister of Defence and Prime Minister and to be nominated as successor. God give him wisdom and equip him to rule his kingdom. With peace and prosperity, McDonald's.”

McDonalds KSA is owned by Mishaal Bin Khalid al Saud, another prince in the huge House of Saud.

The newspaper ad, dubbed “weird” and “surprisingly not a parody” by social media users, was followed up by a tweet.

“We pledge allegiance to His Royal Highness Prince Mohammed bin Salman, and swear loyalty and obedience on the Quran and the Sunnah of his Prophet, praying for Allah to safeguard our beloved kingdom's safety and security," the fast food chain’s account posted.

Many Twitter users jokingly tagged other outlets such as Pizza Hut, KFC, Domino’s and Burger King - only to be bewildered when the latter two followed suit by tweeting supportive messages.

What happened when US officials were asked why they criticised Iran but not Saudi Arabia

Prince Mohammed bin Salman is widely seen as the face of modern Saudi Arabia, and his promotion was expected - if not quite this soon.

His alleged impulsiveness and hawkish stance on Riyadh’s regional rival Iran has alarmed some; considering his youthful age, upon the death of his 81-year-old father, Prince bin Salman is expected to sit on the throne and thus mould Saudi Arabia for decades.