More than 50 people were injured, most of them from tear gas inhalation and some by rubber bullets, in the first major protest against Iraq's fragile, less than year-old government, according to police and medical sources.

More than 1,000 protesters had descended on the main Tahrir Square with Iraqi flags draped over their shoulders or wrapped around their foreheads.

"Those thieves robbed us!" they cried out in condemnation of the political class in Iraq, considered the 12th most corrupt country in the world by Transparency International.

Others were on the streets to protest at the lack of public services, including rampant power cuts, water shortages and unemployment, particularly among youth.

And some carried portraits of Staff Lieutenant General Abdulwahab al-Saadi, who was this week removed from his post in Iraq's Counter-Terrorism Service in a shock move.

Riot police cleared the square a first time but the demonstrators regrouped, making their way to a bridge into the high-security Green Zone where government offices and foreign embassies are present.

Security forces then fired a steady volley of live shots which continued even after the crowds had dispersed into adjacent neighbourhoods.

A security source inside the Green Zone told AFP that reinforcements had been requested to prevent the protesters from entering the area.

The gathering was the biggest demonstration against Prime Minister Adel Abdel Mahdi since he came to power in late October 2018.

The protests over poor services echoed those that engulfed the southern city of Basra last summer.

Despite simmering frustration with the premier, streets in Baghdad had remained relatively quiet, before a confluence of factors apparently reignited public anger.

Graduates have slammed the government for failing to hire them in a country where a vast majority of the labour force is employed by a bloated public infrastructure.

According to the World Bank, youth unemployment in Iraq is running at around 25 percent, double the national average.

Abdel Mahdi has also taken flak over last week's decommissioning of Saadi, feted as a national hero for recapturing Iraqi territory from the Islamic State group.

Since 2004, a year after the US-led invasion that ousted dictator Saddam Hussein, almost $450 billion of public funds has vanished into the pockets of shady politicians and businessmen, according to official figures.