Iraq is on the edge of a mass popular uprising which the government is seeking to stifle through a strictly imposed open-ended curfew and an enforced internet blackout.

Protests, met with a fierce response from the authorities, have gripped Baghdad and spread since Tuesday to southern Iraqi provinces. So far, 19 people have been reported killed, including one policeman, according to authorities. The real total could be higher.

The closing down of the internet has not stopped the protests but has led to them becoming more disorganised and focused in districts of Baghdad away from the centre.

Protesters in the Shia working-class stronghold of Sadr City in east Baghdad attacked municipal offices and set fire to the Dawa party headquarters.

Doctors said some 600 people had been injured on Thursday alone, mostly by rubber bullets fired at the neck or chest.

Sources said that thousands of people from Sadr City had begun a march towards Tahrir Square on Thursday evening, previously the main focus for demonstrators.

The curfew was also being imposed in provincial cities across Shia provinces south of Baghdad.

Iraqi medical officials say 10 people were killed in southern Iraq overnight.

And Iran closed a border crossing with Iraq, citing the “situation” in its neighbouring country.

An Iraqi official says the Khesro border in the eastern province of Diyala will remain closed until further notice.

Security forces enforce a curfew in Baghdad on Thursday (Reuters) (REUTERS)

“I was in Tahrir Square talking to the protesters and they are making all the demands that people have been making since 2003,” Hiwa Osmam, an Iraqi commentator, told The Independent.

“Against corruption, the political parties, the quota system (for different sects and ethnic groups), the lack of education, health concerns and jobs.”

Most of the demonstrators are 20 or under, which means they do not remember a time before the fall of Saddam Hussein in 2003.

The uprising has no discernible leadership, except at a local level, which means that the government has no one to talk to, even if it wanted to.

Parliament speaker Mohammed al-Halbusi invited representatives of the protesters to come to the parliament to discuss their demands, state media reported on Thursday – but it was unclear to whom the invitation was directed.

Moqtada al-Sadr, the populist nationalist cleric, whose followers played a central role in protests in previous years, has tweeted that he supports the movement but “does not want to politicise it”, and is not directly calling on his followers to take part. He is likely acutely aware that the involvement of his followers could alienate many other potential protesters.

The demonstrators appear to have strong support among all sections of society, from working-class Shia slum districts in east Baghdad, to doctors and engineers sending supportive messages.

The streets are almost entirely empty, apart from the occasional bus, potentially used by the security forces.

And the occasional bicyclist – one telling me that while vehicles and pedestrians had been banned, the authorities had said nothing about cycling.

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So far the uprising has been confined to Shia parts of Baghdad, and Shia cities, but there is talk of a demonstration in the Sunni city of Mosul on Friday.

Friday is likely to be a crucial moment for the protests, as it is the traditional day for demonstrations.

So far the government’s over-reaction has succeeded in turning small-scale gatherings against the government into a mass movement, which it will find difficult to resist.

The motives for the government’s hardline actions are mysterious, with speculation that the prime minister, Adil Abdul-Mahdi, is being advised by hawkish military officers, with no understanding of Iraqi politics.