The protest came after the authorities in Basra cancelled a curfew previously announced by their counterparts in Baghdad, only minutes before it had been due to take effect.

Security forces deployed en masse in the area and encircled the protesters, an AFP correspondent at the scene said, but there was no sign of fresh clashes.

Some police and soldiers even laid candles for the demonstrators killed in recent days.

Smoke and flames could be seen rising from the massive government complex, but it was not clear if it was the result of fresh attacks with Molotov cocktails or the remnants of earlier blazes.

The city was largely calm after days of unrest sparked by anger over poor public services and pollution in Basra's water supply, which has put 30,000 people in hospital.

Firefighters were busy all morning trying to extinguish blazes.

They trained their hoses on flames still burning at the provincial headquarters, which protesters have targeted with incendiary devices.

The regional government complex, surrounded by concrete walls, is seen by protesters as a symbol of a corrupt leadership that has failed to deliver basic services in the region.

Oil-rich Basra -- the only province in Iraq with access to the sea -- has been the epicentre of protests over official neglect that have rocked Iraq since early July.

"The people protest and the government doesn't care, treats them as vandals," said Ali Saad, a 25-year-old at the rally.

"Nobody (here) is a vandal: the people are fed up, so yes they throw stones and burn tyres because nobody cares," he told AFP near the building littered with debris.

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".

At least 22 people have been killed in the demonstrations since they erupted in Basra on July 8.

Prime Minister Haider al-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 after elections in May.

Shiite cleric Moqtada Sadr, whose political bloc won the largest number of seats, on Thursday called for a special parliamentary session to address protesters' concerns.

Politicians must present "radical and immediate" solutions at the meeting or step down if they fail to do so, he said.