In Iraq's western Anbar province, tribesmen starting to rebuild have warned they will take revenge on the families of ISIL fighters if they return.

Anbar is the biggest province in Iraq and one of the last places to be freed from ISIL, or the Islamic State of Iraq and the Levant group.

ISIL, also known as ISIS, swept into the province in 2013. The cities of Falluja, Ramadi and al-Qaim soon became urban battlefields.

"We don't want to go back to square one," Omar Shihan al-Alwani, who fought against ISIL, said.

"We're totally against that. If they come back, then blood will flow and neither tribes nor military operations will be able to stop it."

The homes of ISIL family members have been destroyed - a tactic ISIL itself has used in the past.

"We're not against [ISIL family members] returning, but the timing is bad and would risk provoking unrest and a return to bloodshed in the streets," said Omar Ibrahim, a former tribal fighter.

"We the fighters think that families of IS group members should be in a camp under the supervision of Iraqi government and experts such as religious leaders, professors and intellectuals. They should receive daily training sessions."

About 380 families of ISIL fighters including women and children are already detained in two camps across the province. They remain outcasts in Anbar's cities.

Rebuilding Iraq after nearly three years of war with ISIL will cost close to $90bn, according to Iraqi officials attending an international donor conference in Kuwait.

At the conference, Iraq is seeking investment for 157 reconstruction projects including the rebuilding of homes, hospitals and schools.

Throughout Iraq, 2.5 million people were displaced by the fighting. An estimated 138,000 housing units were damaged in the fight against ISIL, with half of them completely destroyed, an Iraqi official said.