At least seven people have been killed and more than 400 injured during two days of anti-government protests across Iraq.

Iraqi Prime Minister Adel Abdul-Mahdi has declared a curfew in Baghdad, preventing almost all movement in the capital until further notice.

Key points: A curfew in Baghdad means almost all vehicles and individuals are "forbidden to move"

A curfew in Baghdad means almost all vehicles and individuals are "forbidden to move" Travellers to and from Baghdad airport, medical workers and religious pilgrims are among those exempted

Travellers to and from Baghdad airport, medical workers and religious pilgrims are among those exempted Protesters are demanding the "fall of the regime"

Mass protests against corruption, unemployment, and the lack of basic services began on Tuesday and quickly spread nationwide, with security forces firing live ammunition, rubber bullets, tear gas, and water cannon to disperse crowds.

An Interior Ministry spokesman said the seven deaths included a child killed when a protester threw a gasoline-filled bottle at a vehicle carrying civilians in Baghdad.

"We are saddened and our heart aches due to casualties among our protesting children and security forces, and the destruction of public property … we have at once started undertaking a professional investigation to determine the causes of the incidents," Mr Abdul-Mahdi posted on Facebook on Tuesday.

Protesters demanded the "fall of the regime", setting government and political party buildings ablaze. ( AP: Hadi Mizban )

Curfews were imposed earlier in three southern cities, while elite counter-terrorism troops opened fire on protesters trying to storm Baghdad airport.

They were also deployed to the southern city of Nassiriya after gunfights broke out between protesters and security forces, police sources said.

"All vehicles and individuals are totally forbidden to move in Baghdad as of 5am today, Thursday, and until further notice," Mr Abdul-Mahdi said in a written statement.

Travellers to and from Baghdad airport, ambulances, government employees in hospitals, electricity, and water departments, and religious pilgrims are exempt from the curfew, the statement said.

It was up to provincial governors to decide whether to declare curfews elsewhere.

Curfews were imposed in Nassiriya, Amara and Hilla as protests that began on Tuesday — over unemployment, corruption and poor public services — escalated.

Demands on Wednesday included the "fall of the regime", and protesters set government and political party buildings ablaze in two other southern provinces.

The slogan, "the people demand the fall of the regime" was popularised during the 2011 Arab Spring uprisings.

All vehicles and individuals are forbidden to move in Baghdad until further notice. ( AP: Hadi Mizban )

Domestic instability coupled with regional tensions could prove to be the final nail in the coffin of Mr Abdul-Mahdi's fragile coalition government, sworn in as a compromise between rival factions after an inconclusive election.

"We are demanding a change, we want the downfall of the whole government," said one protester in Baghdad who declined to identify himself for fear of reprisal.

Any power vacuum in Iraq, should the government be toppled, could prove challenging for the region, given Baghdad's status as an ally of both the United States and Iran, who are locked in a political standoff.

Islamic State militants could also take advantage of any chaos and thousands of US troops are stationed in the country in positions not far from those of Iran-allied Shiite militia.

ABC/Reuters