Egyptian President Mohamed Morsi has said it is an "ethical duty" to support the Syrian people against the "oppressive regime" in Damascus.

His speech at the Non-Aligned Movement (NAM) summit in Tehran on Thursday prompted a walkout by the Syrians.

"Our solidarity with the struggle of the Syrian people against an oppressive regime that has lost its legitimacy is an ethical duty as it is a political and strategic necessity," Morsi said.

"We all have to announce our full solidarity with the struggle of those seeking freedom and justice in Syria, and translate this sympathy into a clear political vision that supports a peaceful transition to a democratic system of rule that reflects the demands of the Syrian people for freedom."