Iran on Monday called the Egyptian army's ousting of president Mohamed Morsi "unacceptable" and said Israel and the West did not want to see a powerful Egypt.
The comments from Foreign Ministry spokesman Abbas Araqchi were more disapproving than his immediate reaction last Thursday, when he merely called for the Egyptian people's "legitimate demands" to be fulfilled.
Iran welcomed the popular overthrow of Hosni Mubarak in 2011, calling it an "Islamic awakening" inspired in part by its own 1979 revolution, and after Morsi's election victory last year it sought to repair its strained ties with Egypt.
However, the two countries now have found themselves supporting opposite sides in the civil war in Syria. While Shi'ite Iran is President Bashar al-Assad's closest Arab ally, largely Sunni Muslim Egypt under Morsi has voiced its support for the mostly Sunni rebel groups seeking to overthrow Assad.
On Monday, Araqchi said: "What is important is giving significance to the legitimate aspirations of the Egyptian people," according to the Mehr news agency.
"However, military intervention in politics is unacceptable and a cause for concern."
Araqchi warned against greater divisions in Egyptian society, adding: "Certainly foreign hands are also at work, and ... the West and the Zionist regime (Israel) will not want a powerful Egypt."
Several dozen people were killed on Monday when Islamist demonstrators enraged by the Morsi's overthrow said the army opened fire on them at the Cairo barracks where he was being held. The military said a group of armed assailants had tried to storm the compound and soldiers returned fire.
Reporting by Yeganeh Torbati; Editing by Jon Hemming and Kevin Liffey