Mohammed bin Salman, who is also Saudi defence minister in the US-allied oil giant kingdom, suggested the Islamic Republic's alleged expansion under Ayatollah Ali Khamenei needed to be confronted. Picture: Presidency Press Service/Pool Photo via AP, File

Tehran - Iran warned Saudi Arabia on Friday that it risks losing credibility on account of its fiery rhetoric, after Crown Prince Mohammed bin Salman called the Islamic Republic's supreme leader "the new Hitler of the Middle East."

Salman, the 32-year-old heir to the Saudi throne, made the comments about Ayatollah Ali Khamenei in an interview with the New York Times, published Thursday.

"His comments are so inappropriate, crude and also partly stupid that he is increasingly losing respectability and credibility in the world," Bahram Ghassemi, a spokesman for the Iranian Foreign Ministry, said in response late Friday.

Ghassemi also said that Saudi Arabia's involvement in domestic Lebanese politics risked the reputation of Riyadh, even among its allies.

"We would therefore advise the crown prince to be careful that, with this kind of politics, he does not experience the same fate as other fallen dictators in the region," the spokesman said in a statement.

Riyadh has been pursuing a newly aggressive foreign policy aimed at combatting Iranian influence and political Islamism since Crown Prince Mohammed's rise to power.

The Sunni-ruled kingdom also faced accusations in recent weeks of having pressured Lebanese Prime Minister Saad Hariri into resigning.