Iraqi Prime Minister Nuri al-Maliki promised police jobs for pro-government fighters in Anbar province Wednesday, as the deputy premier said they aim to cut supplies to gunmen holding one of its cities.

Anti-government fighters seized all of the city of Fallujah and parts of Ramadi, capital of Anbar province, west of Baghdad, where the United Nations says up to 300,000 people have fled a surge in unrest this year.

Clashes in the province have pitted security forces and pro-government tribesmen against jihadist militants and tribal fighters opposed to the authorities.

Police in Anbar "will absorb all the honourable sons of the tribes who stood on the side" of security forces, Maliki said in televised remarks in which he announced measures aimed at addressing the crisis.

It was not clear when the pledge would be implemented, and some tribesmen previously promised jobs after joining forces with the United States against Al-Qaeda militants have faced years of delay in receiving them.

Deputy Prime Minister Hussein al-Shahristani said that to avoid the risk of civilian casualties that would be posed by an armed assault, "the current plan is to restrict the gunmen until (they) run out of weapons and equipment".

Non-military supplies would still be allowed into Fallujah, Shahristani told reporters.

Given militants' long experience with smuggling, the potentially significant quantities of weapons and ammunition already in Fallujah, and the lack of major clashes that would cause fighters to run out of either, the strategy seems unlikely to lead to a swift result.

On Tuesday, the United Nations announced a sharp increase in the number of people displaced in Anbar.

"Over the last six weeks up to 300,000 Iraqis -- some 50,000 families -- have been displaced due to insecurity around Fallujah and Ramadi," a UN refugee agency statement said.

"Most of the displaced have fled to outlying communities in Anbar province to escape the fighting, while 60,000 persons have fled to more distant provinces."

The newly-displaced Iraqis join more than 1.1 million compatriots who fled violence in past years and have still not returned to their homes.

The UN said last month the number of people displaced by the fighting in Anbar was already the highest since the brutal sectarian violence of 2006-2008.

The crisis in the desert province erupted in late December, when security forces dismantled Iraq's main Sunni Arab anti-government protest camp just outside Ramadi.

Anti-government fighters subsequently seized parts of the provincial capital and all of Fallujah to its west, just a short drive from Baghdad.

It is the first time anti-government forces have exercised such open control in major cities since the peak of the deadly violence that followed the US-led invasion of 2003.

At the weekend, Anbar Governor Ahmed al-Dulaimi gave fighters in Fallujah a week to surrender, and said authorities would not negotiate with jihadists involved in the violence.

While government forces have made steady progress in retaking areas of Ramadi, they have largely stayed out of Fallujah for fear that an incursion would spark a drawn-out urban conflict with high numbers of casualties.

Fallujah was a bastion of the Sunni insurgency that followed the invasion, and American forces there saw some of their heaviest fighting since the Vietnam War.

The Anbar standoff comes amid a protracted surge in violence, with security forces also grappling with near-daily attacks nationwide.

There have been calls for the Shiite-led government to address Sunni grievances in order to undermine support for militants, but with an April general election looming, Maliki has generally taken a hard line.