Iraqi demonstrators gather as flames in the southern Iraqi city of Najaf. Haidar Hamdani/AFP

Iraq's protest-hit cities saw one of their bloodiest days yet on Thursday as a government crackdown killed nearly 40 demonstrators following the dramatic torching of an Iranian consulate.

Thursday's violence brought the total death toll since early October to more than 390, with more than 15,000 wounded, according to a media tally.

The highest toll was in the flashpoint southern city of Nasiriyah, where 25 people were killed when security forces used "excessive force" to break up rallies, according to the Iraqi Human Rights Commission.

Another two protesters were killed in Baghdad and ten died in the Shiite shrine city of Najaf, where demonstrators had torched the Iranian consulate late on Wednesday.

Iraqi demonstrators sit on a barrier amid clashes with security forces in Baghdad. Ahmad Al Rubaye/AFP

In Najaf, a city of ancient pilgrimage shrines that serves as seat of Iraq's powerful Shi'ite clergy, the Iranian consulate was reduced to a charred ruin after it was stormed overnight. Protesters accused the Iraqi authorities of turning against their own people to defend Iran.

"All the riot police in Najaf and the security forces started shooting at us as if we were burning Iraq as a whole," a protester who witnessed the burning of the consulate told Reuters, asking that he not be identified.

Another protester, Ali, described the attack on the consulate as "a brave act and a reaction from the Iraqi people. We don't want the Iranians."

But he predicted more violence: "There will be revenge from Iran, I'm sure. They're still here and the security forces are going to keep shooting at us."

So far, the authorities have been unyielding in response to the unrest, shooting dead hundreds of demonstrators with live ammunition and tear gas, while floating proposals for political reform that the protesters dismiss as trivial and cosmetic.

Iraqi demonstrators wearing protective gear rest amid clashes with security forces in Baghdad. AFP

Prime Minister Adel Abdul Mahdi has promised electoral and anti-corruption reform but barely begun delivering while security forces have shot dead hundreds of mostly peaceful demonstrators in the streets of Baghdad and southern cities.

Iraqi PM discusses recent protests in phone call with US Secretary of State

Four Iraqi protesters killed in clashes with security forces

The protests, which began in Baghdad on Oct. 1 and have spread through southern cities, are the most complex challenge facing the Shi'ite-dominated ruling class that has controlled state institutions and patronage networks since the 2003 US-led invasion that toppled long-time Sunni ruler Saddam Hussein.

Young, mostly Shi'ite protesters say politicians are corrupt, beholden to foreign powers — especially Iran — and they blame them for a failure to recover from years of conflict despite relative calm since the defeat of Daesh in 2017.

The street violence in Iraq has left more than 350 people dead and some 15,000 wounded over the past two months.

Military-led 'crisis cells'

Iraqi authorities on Thursday said they had set up "crisis cells" that would be jointly led by military leaders and civilian governors in Iraq's provinces in order to stem spiralling popular unrest, according to a military statement.

Iraqi demonstrators gather as flames in the southern Iraqi city of Najaf. Haidar Hamdani/AFP

The statement said the cells would be headed by provincial governors but that military leaders would be appointed as members and "take over military and security services in (each) province."

Agencies