Lawmakers and ministers will meet on Saturday to discuss the water contamination crisis which has triggered the protests, parliament said in a statement.

Mehdi al-Tamimi, head of Basra's human rights council, said nine demonstrators have been killed since Tuesday in clashes with security forces as anger boils over after the hospitalisation of 30,000 people who had drunk polluted water.

Prime Minister Haider al-Abadi and key ministers are to attend the parliament session, which was demanded by populist cleric Moqtada Sadr, whose political bloc won the largest number of seats in May elections although a new government has yet to be formed.

The rare assault by unidentified attackers on the Green Zone, which houses parliament, government offices and the US embassy, caused no casualties or damage, Baghdad's security chief said.

In Basra, the epicentre of protests that have rocked Iraq since July, demonstrators on Thursday set fire to the local government headquarters and both political party and militia offices.

The fire spread across Basra's massive government complex, with witnesses saying it tore through offices housing state TV channel Iraqiya.

The nearby governor's residence was also set ablaze, AFP journalists reported.

- 'Government doesn't care' -

At least 24 people have been killed in the demonstrations since they erupted in Basra on July 8.

Human rights activists have accused the security forces of opening fire on the demonstrators, while the government has blamed provocateurs in the crowds and say troops have been ordered not to use live rounds.

"The people protest and the government doesn't care, treats them as vandals," said Ali Saad, a 25-year-old at the rally on Thursday attended by thousands of demonstrators.

"Nobody (here) is a vandal. The people are fed up, so yes they throw stones and burn tyres because nobody cares," he told AFP.

Ahmed Kazem, who was also at the protest, urged leaders to respond to the demands of the demonstrators "so that the situation doesn't degenerate".

The 42-year-old said their demands included "public services, water, electricity and jobs".

For Tamimi, the anger on Basra streets was "in response to the government's intentional policy of neglect" of the oil-rich region. "We've been warning the authorities about this for a long time," he said.

Abadi has scrambled to defuse the anger and authorities have pledged a multi-billion dollar emergency plan to revive infrastructure and services in southern Iraq.

But Iraqis remain deeply sceptical as the country remains in a state of political limbo.

Shiite cleric Sadr on Thursday called for politicians to present "radical and immediate" solutions at the emergency meeting of parliament or step down if they fail to do so.

Abadi, for his part, is trying to hold onto his post in the future government through forming an alliance with Sadr, a former militia chief who has called for Iraq to have greater political independence from both neighbouring Iran and the United States.