Egyptian President Mohamed Mursi said bloodshed in Syria would only end if there were "effective interference" from outside.
Mursi told a summit of non-aligned nations in Tehran, one of President Bashar al-Assad's few remaining allies, that Syria needed a peaceful transition to democracy and an end to the current "oppressive regime".
"The bloodshed in Syria is our responsibility on all our shoulders and we have to know that the bloodshed cannot stop without effective interference from all of us," Mursi said.
The Syrian delegation to the NAM summit walked out during Mursi's speech, Al Jazeera television reported.
Mursi, a moderate Egyptian Islamist, said solidarity with the Syrian people "against an oppressive regime that has lost its legitimacy is an ethical duty" and a strategic necessity.
"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."
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