Iran's supreme leader has accused Saudi Arabia of "treason" against Muslims because of its alleged ties to Israel.

Addressing representatives from the Muslim-majority countries in Tehran on Tuesday, Ayatollah Ali Khamenei said "governments that help the United States and cooperate with the Zionist regime to fight Muslim brothers are committing treason, like what Saudis are doing."

However, he also said Iran is ready to adopt a "brotherly attitude" toward countries that have been hostile toward it, and called for Muslim unity.

Iran and Saudi Arabia severed diplomatic ties in 2016 and support opposing sides in the wars in Syria and Yemen.

Iran has seized on media reports that Saudi Arabia is seeking closer ties with Israel in order to join forces against it, something the Saudis deny.