A humanitarian disaster is unfolding in Falluja following a civilian exodus from the Iraqi city, aid workers warn, according to BBC News.

Some 80,000 people have fled during a four-week government offensive to drive back so-called Islamic State fighters, says the UN.

A further 25,000 civilians are likely on the move, the organisation adds.

Aid workers are struggling to provide food, water and medicine to people who are sleeping in the open in hopelessly overcrowded camps outside the city.

"The overwhelming number of people that have come out of Falluja has actually overwhelmed our ability to respond to the people in need," said Nasr Muflahi from the Norwegian Refugee Council (NRC).

"We implore the Iraqi government to take charge of this humanitarian disaster unfolding on our watch," he added.

Iraqi government forces have succeeded in retaking most of Falluja, but fighting continues in some parts of the city, which is just 50km (30 miles) west of Baghdad.

Some residents were reportedly used as human shields by IS to slow the advance of government forces, who are being backed by air strikes from the US-led coalition.

IS militants had captured the northern city in January 2014 and held it for longer than any other city in Iraq or Syria - before the Iraqi army launched an operation to retake it.