Recent clashes in the western Iraq province of Anbar have forced 140,000 people to flee the area, the UN refugee agency UNHCR says.
"Since fighting broke out at the end of last year, more than 140,000 people have been made homeless by fighting according to Iraq's Ministry of Displacement and Migration," UNHCR said in a statement on Friday.
The figure includes more than 65,000 people displaced over the past week alone.
It is the largest displacement of civilians since the country's sectarian war, which caused hundreds of thousands to flee their homes and left thousands dead between 2006 and 2008.
The UN has asked the Iraq government to facilitate humanitarian aid for displaced families in Anbar, according to UNHCR.
"In recent weeks, several bridges leading into the conflict area and communities hosting displaced people have been destroyed, making access difficult," the statement said.
Fighting originally erupted in Ramadi, a key city in Anbar, on December 30, when the Shi'ite-led government cleared out a year-old Sunni Arab protest camp.
The Islamic state in Iraq and the Levant (ISIL), an al-Qaeda-linked militant group, took advantage of the tensions, seizing control of large parts of Anbar province.
The conflict has resulted in violent clashes between ISIL militants and government troops.