Baghdad - Anti-government fighters in parts of the Anbar province have killed three people as the United Nations warned on Friday of Iraq's worst displacement since its brutal 2006-08 sectarian conflict.
More than 140 000 people have fled their homes in the mostly-desert province, which shares a border with Syria, since unrest erupted in late December as security forces and their tribal allies have been locked in a deadly standoff with militants, including those affiliated with the al-Qaeda linked Islamic State of Iraq and the Levant (Isil).
Diplomats and foreign leaders including US President Barack Obama have urged Baghdad to pursue political measures to undercut support for militants, but with an election looming in April, Iraqi Prime Minister Nuri al-Maliki has taken a hard line.
Security forces have mounted a massive operation to retake parts of the Anbar provincial capital Ramadi being held by anti-government fighters and for days have engaged in clashes and exchanged mortar fire.
Shelling which began early on Friday into the Ramadi neighbourhoods of Malaab and Albu Faraj, both out of the government's control, killed two people and wounded 30 others, security and medical officials said.
Government forces and militants also engaged in fire-fights on Thursday evening in Ramadi, but no casualties were reported.
But one person was killed and seven others wounded in heavy shelling late on Thursday in Fallujah, a former insurgent bastion also west of Baghdad that is entirely held by militants.
Fallujah residents blamed the army for the shelling, but defence officials said the military was not responsible.
Parts of Ramadi and all of Fallujah have for weeks been in the hands of anti-government fighters, including members of Isil.
It marks the first time militants have exercised such open control in Iraqi cities since the peak of the violence that followed the 2003 US-led invasion.
The government often says it is fighting al-Qaeda while Fallujah residents and tribal sheikhs have said Isil has tightened its grip on the city. But other militant groups and anti-government tribes have also been involved in battling government forces in Anbar.
On Friday, the UN warned that the continued unrest had sparked Iraq's worst displacement since the country's bloody sectarian war from 2006 to 2008 which left tens of thousands dead.
More than 140 000 had fled their homes since the conflict began, UN refugee agency (UNHCR) spokesperson Peter Kessler said, including more than 65 000 in the past week alone.
"Many civilians are unable to leave conflict-affected areas where food and fuel are now in short supply", he said.
Thousands of displaced have fled to Baghdad and other nearby provinces, but some have travelled as far as the northern Kurdish region, according to UN.
"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.
Fighting originally erupted in the Ramadi area on 30 December, when security forces cleared a year-old Sunni Arab protest camp.
The violence then spread to Fallujah, as militants moved in and seized the city and parts of Ramadi after security forces withdrew.