The Islamic State's (Isis) most senior commander in the besieged city of Fallujah has been killed by a coalition airstrike, says the US military. Operation Inherent Resolve say they have conducted 20 airstrikes in the past few days, claiming the lives of at least 70 militants.

But amongst the jihadists are an estimated 50,000 trapped civilians, who have been told via western leaflet drops to avoid IS areas and put white sheets on their roofs. It is feared that Daesh (Isis) extremists will use civilians as human shields as they crumble to the Iraqi army with aid from the west.

IS took control of Fallujah in January 2014, six months before it established its so called caliphate and it is the longest held city by the terrorist group. Once home to 350,000 people, some of its residents have had to crawl through raw sewage in order to leave the city, according to activists.

The UN says there are reports of people dying of starvation and being killed for refusing to fight for IS. Conditions in the city are deteriorating rapidly, with critical food and medicine shortages, while the prices of essential items have sky-rocketed.

IS positions in villages on the outskirts have fallen in since the beginning of the offensive on 22 May. US Colonel Steve Warren said IS fighter positions and gun emplacements have been targeted in the city with Maher Al-Bilawi killed in the bombardments.

"We are still early in the Fallujah fight so it's unclear how long this battle will last," said Col Warren, who will be soon replaced by Colonel Chris Garver. After Fallujah falls the next step will be Mosul in northern Iraq.

President Barack Obama said that he wants Mosul to be liberated before 2017 and Col Warren said that the coalition plan to take the city soon. He said: "We are going to every city sooner or later," he said. "It's just a case of sequencing."

The assault on Fallujah is being carried out by a combined force of Iraqi army troops, the federal police and Sunni tribal fighters with western assistance. Other militia forces are also said to be involved.

Melissa Fleming, a spokeswoman for the UN High Commissioner for Refugees said to the BBC that horrific crimes have been reported from inside the city. She said: "We have dramatic reports of the increase of the number of executions of men and older boys, refusing to fight on behalf of Isil (Islamic State).

Iraqi troops are fighting against Isis in the besieged city of Fallujah Ahmad al-Rubaye/ AFP