Tens of thousands of protesters opposed to Iraq's prime minister blocked the main highway to Syria and Jordan for the sixth consecutive day on Friday, a move the premier slammed as "unacceptable."

Demonstrators called for Nuri al-Maliki to resign after he criticised protesters in a call for dialogue, while security forces barred Baghdad-based journalists from entering the province where the biggest protests were being held.

Major demonstrations have taken place this week in the mostly-Sunni Arab provinces of Nineveh and Salaheddin, but the biggest rallies have been in Anbar, west of Baghdad, following the arrest of at least nine of Sunni Arab Finance Minister Rafa al-Essawi's guards.

On Friday, protesters in Anbar provincial capital Ramadi called for the release of prisoners they allege were arrested on sectarian grounds by Iraq's Shiite-led authorities, while some held banners that read: "Get out, Maliki".

"The Iraqi people are united," said a statement issued by one of the groups organising the protest, the Coordination Committees of the Revolution, referring to Maliki as "a sectarian prime minister."

Among the protesters were residents of the northern Kurdish region, the southern port city of Basra, and the main northern city of Mosul.

Protesters have been demonstrating in Ramadi since Sunday, blocking the main highway to Syria and Jordan for the past six days.

Although local police were at the scene of the Friday protest, searches of those entering the rally site were carried out by organisers, and no soldiers appeared to be present.

Army units did, however, bar Baghdad-based journalists from entering Anbar province, holding teams from AFP and other media at a checkpoint between Baghdad and Ramadi for more than five hours.

They also confiscated their press badges, promising to return them only if they turned back to Baghdad.

A senior security official said that there were "strong preventative measures to protect the demonstrators", but AFP journalists witnessed dozens of cars pass through the checkpoint where they were held with no questioning whatsoever.

Maliki argued in a speech in Baghdad that countries "must rely on civil means of expression," adding that "cutting roads and stirring sectarian strife" is "not acceptable".

He said that it is instead better that "we talk and we agree at the table of brotherhood and love in ending our problems and differences, and that we listen to each other".

The demonstrations began on Sunday after Essawi's guards were arrested by security forces on December 20 on terrorism charges, leading the minister, a prominent member of the secular, Sunni-backed Iraqiya bloc, to call for Maliki to resign or be removed.

Iraqiya and other members of Maliki's unstable national unity government have accused him in the past year of concentrating power in his hands and moving towards a dictatorship.

The arrest of Essawi's guards came almost exactly a year after Sunni Arab Vice President Tareq al-Hashemi's guards were arrested and accused of terrorism.

An arrest warrant was also issued for Hashemi, like Essawi, an Iraqiya member, who fled to Iraq's autonomous Kurdistan region and eventually to Turkey, saying the charges against him were politically motivated.

Hashemi has since been given multiple death sentences in absentia on charges including murder, while death sentences have also been handed down against his guards.