At least two protesters have been killed and dozens injured in central Baghdad when Iraq's security forces launched tear gas canisters to disperse demonstrators trying to breach the capital's Sinak bridge, according to activists and officials.

Riot police on Friday hurled sound bombs and fired tear gas after protesters attempted to breach cement barriers previously erected by security forces, three activists and a security official told The Associated Press news agency.

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A medical source told Reuters News Agency that one of those killed had a tear gas canister launched directly at his neck.

"Saboteurs attacked the barricades in the Sinak bridge area and security forces have been using non-lethal methods to stop them for hours," said a spokesman for the prime minister.

The bridge is close to the capital's central Tahrir Square where thousands have been camped out for months, with recent clashes causing the authorities to restrict access to the crossing.

Mass protests have gripped Iraq since October 1 with protesters demanding sweeping reforms, new leadership and snap elections.

They see their political system as profoundly corrupt and keeping most Iraqis in poverty.

More than 450 people have been killed since the demonstrations erupted. Gunmen killed two local journalists covering protests last Friday in the southern city of Basra.

Despite numbers recently dwindling, protesters took to the streets again last week, determined to keep up the momentum of their protests despite attention turning to the threat of a US-Iran conflict after Washington killed Tehran's top general in an air strike inside Iraq.

In an effort to bring back focus to the goals of the protest movement, anti-government protesters in the southern city of Nasirya gave the government a week's deadline to take serious steps to implement changes. The deadline runs out early next week.