Desperate Iraqi families attempting to flee besieged Fallujah, making the deadly crossing over the Euphrates, end up trapped between the Iraqi government advance and Isis snipers.

Reuters reported that at least four had died in the attempt to make the crossing on makeshift rafts. Video shows the Fallujah citizens using a system of ropes to cross the river as worried bystanders observe from the other side.

At one point a man can be seen bailing out his improvised vessel while in other images young children can be seen attempting to swim across the Euphrates while they are carried along by the current. In some instances the desperate civilians were reported to have used refrigerators and cupboards to cross the river.

Reports have said as many as 12 were killed by Isis fighters who had fired upon anyone trying to leave Fallujah. The extremist group was said to have set up IEDs and other booby-traps on all routes out of the city, forcing residents into the river.

The Norwegian Refugee Council has warned that a humanitarian crisis is underway in Fallujah. "An unidentified number of civilians have been shot and killed trying to cross the river," it said.

Nasr Muflahi, Iraq's country director of NRC, said in a statement: "Our biggest fears are now tragically confirmed with civilians being directly targeted while trying to flee to safety.

"This is the worst that we feared would happen to innocent men, women and children who have had to leave everything behind in order to save their lives."

The United Nations has warned Fallujah's 50,000 inhabitants are being used as human shields by Islamic State, as fighting continues.

It has also emerged that civilians caught up in the advance by Iraqi Army and so-called Popular Mobilisation Forces risk torture at the hands of pro-government Shia militia.

According to Yahya al-Muhamadi, an Anbar council member working with displaced civilians and quoted by the Associated Press , five of those detained died while in the group's custody.