Three anti-government protesters have been killed in heavy clashes in central Baghdad, hours after four demonstrators died in overnight violence.

Security and medical officials said the latest deaths occurred on Rasheed Street as security forces used tear gas, sound bombs and live rounds to disperse protesters.

Two of them were killed when they were hit by tear gas canisters, and the third was killed by live ammunition. The clashes took place near Ahrar Bridge.

It came after altercations on bridges left four dead and 44 injured.

Iraq Protests
Protesters receive treatment at Tahrir Square in Baghdad after renewed clashes with security forces (Ali Abdul Hassan/AP)

One protester was killed when security forces used live rounds to repel demonstrators on Ahrar Bridge, while another died when a tear gas canister was fired on Sinak Bridge, hitting him in the head.

Two protesters later died from injuries sustained in the violence.

Protesters have been occupying parts of Baghdad’s three main bridges – Sinak, Ahrar and Jumurhiya – leading to the heavily fortified Green Zone, the seat of Iraq’s government.

Tents have been set up under the bridges and also on central Tahrir Square, the epicentre of the protest movement.

Fighting also resumed overnight in the Shia holy city of Karbala, south of Baghdad, between protesters and security forces.

Iraq Protests
Anti-government protesters have set up camp on bridges leading to the Green Zone in Baghdad (Khalid Mohammed/AP)

There, protesters threw fire bombs at security forces while anti-riot police responded by hurling stones at the demonstrators.

At least 320 protesters have been killed and thousands more have been injured since the unrest began on October 1, when demonstrators took to the streets in Baghdad and across Iraq’s mainly Shia south to decry rampant government corruption and a lack of basic services despite Iraq’s oil wealth.

The leaderless movement seeks to dismantle the sectarian system and unseat the government, including Prime Minister Adil Abdul-Mahdi.