ISIL terrorists are using civilians as human shields in Fallujah, directly targeting all those who attempt to flee the Iraqi city, an aid group said.

ISIL terrorists are using  civilians as human shields in Fallujah, directly targeting all those who attempt to flee the Iraqi city, an aid group said.

"Reports from families that NRC has been in touch with describe that civilians trying to cross the Euphrates River in order to flee the fighting are being targeted by armed opposition groups," the Norwegian Refugee Council (NRC) said in a statement on Sunday.

In footage broadcast on state television on Wednesday, Iraqi Prime Minister Haider al-Abadi announced that the military offensive to liberate Fallujah has been slowed down due to fears for the safety of civilians being used as human shield in the city.

He also said that safe corridors have been established to allow some civilians to exit.

The NRC notes that even though the majority of Fallujah's population is believed to have fled, as many as 50,000 civilians, including 20,000 children, are thought to be trapped in the city.

"Our biggest fears are now tragically confirmed with civilians being directly targeted while trying to flee to safety," said NRC country director Nasr Muflahi said.

"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."

ISIL overran Fallujah in the western Anbar province in January 2014, six months before the terror group proceeded with its offensive, taking more areas in Iraq.

On May 23, the Iraqi military started a large-scale push to drive out the militants from Fallujah, located 65 kilometers (40 miles) west of the capital, Baghdad.