The ruling against Salman, who headed the now-banned Al-Wefaq movement, has been called a travesty by rights groups.
Iran's foreign ministry spokesman Bahram Ghasemi said the verdict "leaves no doubt for the international community that the government of Bahrain... intends to intensify its suppression."
He called on Bahraini officials to "put aside their police state methods and use real and serious dialogue with the opposition and critics," in a statement published late Sunday.
Ghasemi also said Manama should refrain from issuing "inhumane verdicts against its people".
Salman and the two aides had been acquitted by the high criminal court in June, a verdict the public prosecution appealed.
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