Nearly 45 people were killed and hundreds wounded across the south on Thursday, according to medical sources, a day after the torching of Iran's consulate in the shrine city of Najaf.

At least 16 of them died in Najaf, where on Friday a massive funeral procession wound its way through the streets of the holy city, carrying coffins.

Further south in Nasiriyah, demonstrators rallied in one of the main squares calling for the "fall of the regime", a day after 25 people died there.

Two other protesters were killed in the capital, Baghdad.

Baghdad and the south have been rocked by the worst street unrest since the 2003 US-led invasion that toppled Saddam Hussein, with a protest movement venting fury at the government and its backers in neighbouring Iran.

Thursday's violence brought the total death toll since the start of October to nearly 400, with more than 15,000 wounded, according to an AFP tally.

The escalation came after crowds outraged at Iran's political influence in Iraq stormed and burned down the Islamic republic's consulate in Najaf, blaming it for propping up a government which they seek to topple.

In response, Prime Minister Adel Abdel Mahdi ordered military chiefs to deploy in several provinces to "impose security and restore order".

Amnesty International denounced a "bloodbath" in Nasiriyah.

"The scenes from Nasiriyah this morning (Thursday) more closely resemble a war zone than city streets and bridges," said Lynn Maalouf of the London-based rights group.

"This bloodbath must stop now," she said.

Protesters are seeking an overhaul of the ruling elite which they accuse of corruption and embezzling state funds, in a country scarred by decades of conflict and where infrastructure is failing.