More than 13,000 families have fled Fallujah, NGOs said yesterday, warning of a "critical" humanitarian situation as masked gunmen locked in a days-long standoff with Iraqi troops hold the city. Despite traffic police returning to its streets, some shops reopening and more cars being on the roads, Fallujah was still hit by clashes and shelling, after an al-Qaeda-linked group urged Sunnis to keep fighting the Shiite-led government. Fallujah and parts of nearby Ramadi, both in the western province of Anbar which borders Syria, have been outside government hands for days - the first time militants have exercised such open control in major cities since the height of the insurgency that followed the US-led invasion in 2003. The Iraqi Red Crescent yesterday said it had provided humanitarian assistance to more than 8,000 families across Anbar but added that upwards of 13,000 had fled and were living with relatives, or in schools or other public buildings. "There is a critical humanitarian situation in Anbar province which is likely to worsen as operations continue," Nickolay Mladenov, the UN special envoy to Iraq, said in a statement. "The situation in Fallujah is particularly concerning as … stocks of food, water and life-saving medicines begin to run out." Uniformed traffic police, whose sole responsibility is directing vehicles and controlling intersections, were back on the streets in several parts of central Fallujah early yesterday, the AFP news agency reported. They were apparently on duty with the approval of the gunmen. The gunmen were deployed in areas around the edge of Fallujah, at the entrances of neighbourhoods, and on bridges - including one from which the bodies of American contractors were infamously hung in 2004, prompting the first of two assaults by United States forces that year.