Protesters clashed with anti-riot police Friday in Iraq despite the prime minister's pleas for patience and an internet blackout on the fourth day of mass rallies that have left 73 dead.

Many were awaiting a signal in the midday sermon of Grand Ayatollah Ali Sistani, Iraq's highest Shiite Muslim authority, that would influence the revolt in the predominantly-Shiite areas.

Before dawn, Prime Minister Adel Abdel Mahdi appeared in his first televised address since the protests kicked off on Tuesday, asking for more time to implement a reform agenda in a country plagued by corruption and unemployment after decades of conflict.

As the pre-recorded address played on state television, heavy gunfire rang out across Baghdad and two more protesters and one police officer were killed in the south.

By sunrise, security forces were out in force across the capital in a bid to tighten a curfew announced the previous day, blocking off access to the emblematic gathering place of Tahrir (Liberation) Square.

But dozens of protesters amassed in a main thoroughfare nearby, descending from trucks and buses wearing masks and carrying Iraqi flags.

"We heard Abdel Mahdi's speech yesterday. These are promises we've been hearing for more than 15 years," a 32-year-old protester who identified himself as Sayyed.

"They change nothing and they won't get us off the streets. Either we die or we change the regime," he told AFP.

Demonstrations over corruption, unemployment and lacking services first broke out in Baghdad and have since spread to the Shiite-dominated south, while the northern and western provinces have remained relatively quiet.

They are unprecedented because of their apparent spontaneity and independence in a country where rallies are typically called by politicians or religious figures.

Instead of matching posters or party insignia, protesters have brandished Iraqi flags and banners with uncoordinated slogans and hashtags.

'No magic solutions'

Riot police have unleashed water cannons, tear gas, rubber bullets and live fire to clear the streets of protesters, who amassed despite curfews and an internet blackout across three-quarters of Iraq since Wednesday.

The clashes have left a total of 44 people, including four policemen, dead.

But in his speech on Friday, Abdel Mahdi insisted security forces were abiding by "international standards" in dealing with protesters and rejected the"politicisation" of protests.

He described the clashes as "the destruction of the state, the entire state", but refrained from directly addressing protesters' demands.

Instead, the embattled premier broadly defended his government's achievements and pledged monthly stipends for families in need, while asking for more time to implement the reform agenda he promised last year.

"There are no magic solutions," he said.

A major turning point on Friday will be the weekly sermon by Sistani that could either demand protesters clear the streets or add fuel to the fire.

It carries the final word even at the highest level of Iraq's governments: in 2014, Sistani put an end to previous prime minister Nouri al-Maliki's term.

The trajectory of the protests could also be heavily influenced by firebrand cleric Moqtada al-Sadr, who has called for "a general strike".

Sadr was behind the last round of major protests in Baghdad in 2016, when his supporters stormed the Green Zone which is home to some ministries and embassies.

The United Nations, European Union and Britain have all appealed for calm, while rights group Amnesty International condemned the response to protests.

"It is outrageous that Iraqi security forces time and again deal with protesters with such brutality using lethal and unnecessary force," said Amnesty's Lynn Maalouf.

She said the internet blackout was a "draconian measure... to silence protests away from cameras and the world's eyes".