Hundreds of Iraqis protested in central Baghdad on Sunday in defiance of a crackdown by the authorities that killed scores of people over the weekend.

Security forces fired tear gas across barricades erected by protesters on a bridge leading to the fortified Green Zone which houses government offices and diplomatic missions, according to Reuters news agency.

More than 60 people were killed during demonstrations on Friday and Saturday which drew thousands of protesters and led to clashes with the security services and militia groups. It brings the death toll from protests this month to about 220.

Reuters cited security sources as saying that elite counter-terrorism forces had been deployed to Baghdad and given instructions to "use all necessary measures" to end the protests.

It also reported that counter-terrorism forces beat and arrested dozens of protesters in the southern city of Nasiriya on Saturday night.

This is the second flare up of protests in October after an explosion of popular anger against a regime held responsible for rising poverty, corruption and unemployment that lasted several days earlier in the month. The unrest started in Baghdad but quickly spread to the Shia-majority south of the country where, reports say, most of the deaths have taken place.

The security services used curfews, internet shutdowns and live ammunition to quell the earlier protests, killing about 150 people and wounding thousands. A government-appointed official inquiry later concluded the authorities had used excessive force and recommended the firing of security chiefs. Eight members of the security services were also killed in the clashes.

The civil unrest, which transcends sectarian divisions between Shia and Sunni Muslims, represents the biggest challenge faced so far by the government of Adel Abdul Mahdi, the prime minister, an independent who emerged as a compromise candidate after elections last year.

Mr Abdul Mahdi has acknowledged the protesters' grievances and offered a welfare package in a bid to quell the unrest, but said his administration had inherited a host of problems for which there is "no magic solution". He promised a government reshuffle over the weekend but it has not been enough to pacify protesters fed up with what they view as an inept political establishment.

Sixteen years after the US invasion that toppled the dictatorial rule of Saddam Hussein, Iraq remains unstable. The state is riddled with corruption and the economy is unable to provide prosperity and jobs for the country's youths, despite its oil wealth.

The demonstrators are mostly young men who organise on social media, demanding employment and services such as adequate water and electricity.

More than half of all Iraqis are under the age of 24 and some 20 per cent of Iraqis between the ages of 15 and 24 are not in education, training or employment, according to the World Bank.