"No to Israel! No to America!" chanted demonstrators gathered after Friday prayers in the Sadr City district of Baghdad, Moqtada Sadr's stronghold in the capital, holding umbrellas to shield themselves from Iraq's scorching summer sun.

"It is an unjust war... Israel has no right" to hit Iran, said protester Abu Hussein.

"Israel is not in it for the (Iranian) nuclear (program). What Israel and the Americans want is to dominate the Middle East," added the 54-year-old taxi driver.

He said he hoped Iran would come out of the war victorious, and that Iraq should support its neighbour "with money, weapons and protests".

In Iraq's southern city of Basra, around 2,000 people demonstrated after the prayers, according to an AFP correspondent.

Cleric Qusai al-Assadi, 43, denounced Israel's use of Iraqi airspace to bomb Iran. "It is a violation of Iraq's sovereignty," he said, warning against "a third world war against Islam."

Echoing the views of Sadr, Assadi said that Iraq should not be dragged into the conflict.

In a statement earlier this week, Sadr condemned "the Zionist and American terrorism" and the "aggression against neighbouring Iran, Palestine, Lebanon, Syria and Yemen", referring to Israel's military operations in those countries.

Sadr, who once led a militia fighting US-led forces after the 2003 invasion, retains a devoted following of millions among the country's majority community of Shiite Muslims, and wields great influence over Iraqi politics.

He has previously criticised Tehran-backed Iraqi armed factions, who have threatened US interests in the region if the United States were to join Israel in its war against Iran.

On Friday, Israel launched a surprise attack targeting Iran's military and nuclear sites and killing top commanders and scientists, saying it was acting to prevent Iran from obtaining a nuclear weapon, an ambition Tehran denies having.

The assault has prompted Iran to retaliate with barrages of missiles aimed at Israel, with residential areas in both countries suffering.

Iraq is both a significant ally of Iran and a strategic partner of Israel's key supporter, the United States, and has for years negotiated a delicate balancing act between the two foes.

It has only recently regained a semblance of stability after decades of devastating conflicts and turmoil.