In the southern city of Nasiriyah, demonstrators said they would remain in the streets "until the regime falls".

And in Baghdad, some 300 people descended on the iconic Tahrir Square, carrying Iraq's tricolour flag and calling for the country's entrenched political class to be "uprooted".

"They're all thieves!" some yelled, while others chanted: "Baghdad is free, Iran get out!".

Tehran holds significant sway in Iraq as does its arch-foe Washington -- and protesters and government officials alike have accused foreign powers of interfering in the movement.

Demonstrations erupted in the first week of October with calls for an end to widespread corruption and unemployment, then evolved into demands for a political overhaul.

But they were met with a tough response, with 157 people killed in six days, according to a government toll.

Activists had called for a resumption of protests on Friday, which marks the one-year anniversary of Prime Minister Adel Abdel Mahdi's government and a deadline set by Iraq's top religious authority for him to introduce reforms.

The country was on a knife's edge on Thursday, with many stockpiling food, petrol and other supplies.

The United Nations had urged the government to "draw lessons learned" from the earlier bloodshed.

But Thursday's demonstrations began ahead of schedule and appeared to be peaceful, with no reported incidents of violence.

Interior Minister Yassin al-Yasseri was in Tahrir Square to reassure protesters that security forces would "protect" them, his office said in a statement.