More than 140,000 people have fled their homes in the Iraqi cities of Fallujah and Ramadi since December when anti-government fighters occupied parts of both cities, according to the UN refugee agency.
On Friday, the UN warned that the continued unrest in Anbar province had sparked Iraq's worst displacement since sectarian violence from 2006 to 2008 left tens of thousands dead.
More than 65,000 people have fled their homes in the past week alone, UN refugee agency (UNHCR) spokesman Peter Kessler said in Geneva.
"Many civilians are unable to leave conflict-affected areas where food and fuel are now in short supply," he said.
"People are reportedly without money for food and lack suitable clothing for the rainy conditions. Children are not in school and sanitary conditions, particularly for women, are inadequate," said Kessler.
Thousands of displaced people have fled to Baghdad and other nearby provinces, but some have travelled as far as the northern Kurdish region, according to the UN.
Fighting erupted in the Ramadi area on December 30, when security forces cleared a year-old Sunni Arab protest camp.
The violence then spread to another city of the western province, Fallujah, as fighters seized the centre of the city and parts of Ramadi after security forces withdrew.
Fighting escalated in the mostly-desert province after security forces launched an offensive against fighters, including those affiliated with the al-Qaeda-linked Islamic State of Iraq and the Levant (ISIL).
Foreign leaders including US President Barack Obama have urged Baghdad to pursue political measures to undercut support for armed groups, but with an election looming in April, Prime Minister Nouri al-Maliki has taken a hard line.
Diplomats and foreign leaders, including Obama and UN chief Ban Ki-moon, have pushed Maliki, a Shia, to do more to work with Iraq's Sunni Arab minority and pursue political reconciliation.
But while the government has made some concessions to the disaffected minority in recent months, it has mostly focused on wide-ranging security operations.
Security forces have mounted a massive operation to retake parts of the provincial capital Ramadi, and for days have engaged in clashes and exchanged mortar fire.
Shelling which began early on Friday of the Ramadi neighbourhoods of Malaab and Albu Faraj, both out of the government's control, killed two people and wounded 30, security and medical officials said.
Fallujah residents blamed the army for the shelling, but defence officials said the military was not responsible.