The Iraqi military said that it is preparing to storm Isis-held Fallujah, the city that was the scene of the bloodiest fighting for US Marines during the Iraq War.

The military statement gave no timeline for the operation but said counter-terrorism forces, police, tribal fighters and popular mobilisation units - which include an array of Shia militias - will be involved.

US-supplied F-16s had already begun bombing targets in the city, the statement said. Civilians were urged to stay away from Isis (Islamic State) headquarters.

Few expect an easy fight. Isis militants have dug in and built defences in the city since capturing it more than two years ago, the first in the country to fall to the extremist group.


1 Fallujah has long been considered a hotbed of rebellion and extremism
2 Even the heavyhanded Saddam Hussein struggled to control its tribes
3 US Marines fought Sunni insurgents during two battles for the city in 2004
4 The second battle marked the heaviest urban combat for American troops since Vietnam, claiming the lives of nearly 100 service members.

It's not an order of battle that correlates to US military policy, which had focused on an offensive targeting Mosul, the Isis-held city farther north.

US President Barack Obama has said he expects the recapture of Mosul to be close to complete by the end of the year. But a drawn-out battle for Fallujah could delay the already stuttering build-up to that offensive.

There has, however, been a growing push within the Iraqi military to recapture Fallujah first.

Some of the pressure comes from Shia militia forces beseiging the city, which lies 65km west of Baghdad. The heavy presence of those Shia militia fighters, who view much of the Sunni population as sympathetic to the Isis militants, has raised fears of sectarian reprisal killings during any operation, though military commanders said militias would stay at the city's outskirts.

"Your sons, the heroic fighters in the armed forces, are preparing to achieve a new victory," Saad al-Hadithi, a spokesman for Prime Minister Haider al-Abadi said in a statement. "Liberating the city of Fallujah will be a victory for all Iraqis and will pave the way for the return of stability and normalcy to the province of Anbar."

In a speech at the weekend Abadi had mentioned a forthcoming offensive for Fallujah and the remaining militant-held areas of Anbar province - and "then Mosul". Today Abadi held a meeting with legislators and local officials from the province to inform them of military plans and efforts to protect civilians.

A recent wave of bombings in Baghdad has added weight to the calls for those arguing that a Fallujah operation is more pressing than Mosul, with a militant hub so close to the capital putting civilians at risk.

Iraqi forces have already scored a string of victories against Isis fighters in the province, most recently taking the desert smuggling town of Rutba, with commanders arguing they should build on successes there.

Sunni leaders from the province have also lobbied for an offensive, saying the continued siege of the city by military and militia forces is causing a humanitarian crisis inside as many as 60,000 residents remain trapped without access to food and medical supplies.

"We call on all citizens who are still inside Fallujah to prepare to get out," the military statement said, adding that secure routes would be organised later. Citizens who cannot should "raise a white flag" on their homes, it said.

However, Jumaa al-Jumaili, a commander with local Sunni tribal forces, said Isis was not allowing anyone to leave the city in order to use residents as human shields.

"They desperately want to keep Fallujah because of its symbolic importance and location close to Baghdad," he said. "But it's almost besieged from all sides."

He said that Shia militia forces had agreed to fight on the outskirts of the city. "We want the people of Fallujah to rise against (Isis)," he said, adding that the presence of Shia militia forces in the city wouldn't help that aim.

Lieutenant General Abdulwahab al-Saedi, who will be leading the operation for Iraq's counter-terrorism forces, said the army, police and Shia militias will fight only on the outskirts of the city while his forces will "storm the centre". The operation will be "very, very soon," he added, though refusing to give a timeline. He said that the US-led coalition will give air support and that the battle will be "difficult but not impossible".

"We do think they can do it," said Colonel Steve Warren, a Baghdad-based spokesman for the US military, confirming that the coalition will provide air support.