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."
His comments sparked a walkout by the Syrian delegation.
Syria's Foreign Minister Walid Muallem said Morsi's speech "incites continued bloodshed in Syria".
Al Jazeera's Imran Khan, reporting from the summit, said: "Morsi's comments have caused an unease feeling, especially for the Iranians who are close to Syria."
Morsi's visit to Iran is the first by an Egyptian leader since 1979.
NAM was established in 1961 by countries that wanted to counterbalance the dominance of the US and Soviet Union during the Cold War.
It meets once every three years but its relevance on the international stage has declined significantly since the end of the Cold War and the fall of the Soviet Union.
The crisis in Syria is on the agenda for the two-day summit, as are human rights and nuclear disarmament.
'Overt dicatorship'
Earlier Ayatollah Ali Khamenei, Iran's supreme leader, opened the summit by attacking the "overt dictatorship" of the UN Security Council in a speech.
"The UN Security Council has an irrational, unjust and utterly undemocratic structure, and this is an overt dictatorship," he said.
Iran is in a showdown with the UN over its disputed nuclear programme, which has resulted in four sets of Security Council resolutions imposing sanctions on it for pursuing uranium enrichment.
Khamenei charged that "the control room of the world [the Security Council] is under the control of the dictatorship of some Western countries" - implying the permanent council members France, Britain and US.
State television showed Ban looking nonplussed as Khamenei delivered his speech.
The NAM has long championed a reform of the UN to take power away from the Security Council and bolster the say of the General Assembly, where its members are better represented.
Khamenei's criticism of the UN's top table followed a meeting he had with Ban on Wednesday in which the UN leader bluntly told Iran to take "concrete" steps to ease the showdown over the nuclear issue.
Nuclear issue
Khamenei also told delegates that "I insist that the Islamic Republic of Iran is never seeking nuclear weapons", calling them "a major and unforgivable sin".
But he said Iran would "never give up the right to peaceful nuclear energy".
Ban urged Iran to comply with UN resolutions, demanding it curb its nuclear activities, saying that heightened international rhetoric over the issue risked degenerating into "war".
He said Iran should build confidence in its nuclear programme by "fully complying with the relevant [UN] Security Council resolutions and thoroughly co-operating with the IAEA."
Otherwise, he cautioned, "a war of words can quickly spiral into a war of violence".
He arrived on Wednesday and met Khamenei and Mahmoud Ahmadinejad, Iran's president.
Ban has not shied from drawing attention to Iran's human-rights record, expressing "serious concerns" about them.
Earlier Ayatollah Ali Khamenei, Iran's supreme leader, opened the summit by attacking the "overt dictatorship" of the UN Security Council in a speech.
Now, I don't know much about Iran's government structure, but if you are a Supreme Leader, ummm you might be a dictator?
So, because I know nothing of this, I turn to the Google and the Supreme Leader ... "has the power to appoint and dismiss the leaders of the judiciary, the state radio and television networks, and the supreme commander of the Islamic Revolutionary Guard Corps. He also appoints six of the twelve members of the Council of Guardians, the powerful body that oversees the activities of Parliament and determines which candidates are qualified to run for public office." www.iranchamber.com/government/articles/structure_of_power.php
So, when is the war? I'm seriously just waiting for a war to break out here. Is this sad?
Walkouts like this bug me. You can massacre towns full of babies no problem, but you can't take a good old fashioned talking-to? I get that it's symbolic, but still. Puh-leeze.
I just wanted to say that I read this. I have nothing substantial to contribute, though.
LOL
The news about Syria in the past few days is a bit unnerving. Basically the feeling is that the rebels overreached and can't maintain their current positions. I've also read there is suspicion that Assad and his group have contingency plans to flee to the mountains, which sounds a bit James Bond villain-ish to me.
Syria is a mess. I tell myself I'm getting more isolationist as I get older, yet I was all "invade that fucker!!" about Libya last year and think I feel that way about Syria, especially when I read about the atrocities against civilians.