The six-nation Gulf Cooperation Council on Monday protested at what it termed "contradictory" signals coming from Iran since its nuclear accord struck with world powers last week.
GCC chief Abdellatif Zayani said Iranian President Hassan Rouhani was offering to turn a "new page" with its Arab neighbours while its supreme leader Ayatollah Ali Khamenei had pledged to keep up support for Shiite opposition groups.
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Such messages sent out "contradictory" signals, he said in a statement, adding that Khamenei's comments amounted to "unacceptable interference" in the affairs of Arab states.
Khamenei, in a speech on Saturday, said Iran's agreement with world powers would not alter its support for the governments of Syria and Iraq nor its backing of "oppressed people" in Yemen and Bahrain, and the Palestinians.
The speech was contrary to "the principles of good neighbourliness", charged Zayani, vowing that the Arab monarchies of the Gulf would "continue to defend their interests".
Majority Sunni Gulf countries have reacted with caution to the nuclear deal, believing it will only embolden Tehran's Shiite leaders.