The anti-regime demonstrations had been overshadowed recently by spiralling tensions between Tehran and Washington, which led each country to carry out strikes against the other's assets in Iraq over the last week.

Fearing their movement would be eclipsed by war, Iraqi activists posted calls on social media in recent days for a mass protest on Friday, which marked the inverse date, 10/1, of the first rallies on October 1, or 1/10.

Iraqis turned out across the country, with hundreds streaming into the capital's Tahrir Square, the epicentre of the anti-regime movement, AFP journalists said.

"Screw Iran! Screw America!" they cried out in the iconic square, still lined with tents and stalls set up three months ago.

Thousands more took to the streets in the country's Shiite-majority south, including the main protest hotspots of Diwaniyah, Nasiriyah, the oil-rich port city of Basra and the twin shrine cities of Najaf and Karbala.

Protesters in Karbala clashed overnight with security forces and others were arrested in Basra on Friday.

"By relaunching the protests, we're showing our commitment to the demands of the October revolution: that our leaders stop monopolising our country's resources," said Haydar Kazem, protesting in Nasiriyah.

Iraq is OPEC's second-largest crude producer, but one in five people live in poverty and unemployment is rife among youth, according to the World Bank.

Transparency International ranks Iraq the 12th most corrupt country in the world.

Outraged by government graft and inequality, Iraqis launched an anti-regime protest movement in October that saw unprecedented numbers hit the streets.

But the rallies were met with violence, with nearly 460 people killed and more than 25,000 wounded since they began.

The protests began to slip out of the spotlight in late December after a US contractor was killed in a rocket attack on a northern Iraqi military base where American and other international troops are stationed.

The US blamed a hardline group in the Hashed al-Shaabi, a military network incorporated into the Iraqi state, and launched an air strike that killed 25 Hashed fighters.

Supporters of the group then besieged the US embassy in Baghdad and days later, the US killed a top Iranian commander and the Hashed's deputy chief in a drone strike outside the Baghdad airport.

In retaliation, Iran launched ballistic missiles on Iraqi bases where US and coalition forces are stationed.

The rallies persisted throughout the developments, but shifted to include calls for Iraq to be spared any conflict between Iran and the US, both of them allies of Iraq.