Iraq's Fallujah operation slowed by civilians, ISIS resistance

Iraqi forces stalled at the fringes of Fallujah, slowed in their advance on Wednesday by concerns over the fate of trapped civilians and resistance from the Islamic State group.

Fighting also raged hundreds of kilometres further up the Euphrates Valley in Syria, as US-backed Kurdish and Arab fighters opened a new front against the jihadists in the strategic Manbij pocket on the Turkish border.

After a week of shaping operations aimed at sealing the siege of Fallujah, which lies just 50 kilometres west of Baghdad, elite forces launched a new, more aggressive phase on Monday morning.

But they have so far been unable to reach the city centre and battle IS fighters in the streets of one of their historical strongholds.

Prime Minister Haider al-Abadi said concern for the estimated 50,000 civilians the United Nations has said IS was using as human shields was slowing progress.

"It would've been possible to end the battle quickly if protecting civilians wasn't one of the foundations of our plan," he told commanders in comments broadcast by state television.

Iraq's parliament speaker, Salim al-Juburi, held talks with officials from Anbar province, where Fallujah is located, as well as commanders and tribal leaders on the humanitarian issue.

He discussed "ways of rescuing the families being held hostage and opening safe corridors for them," his office said in a statement.

Inside Fallujah, trapped residents were under increasing pressure from worsening shortages and nervous IS fighters preparing for a desperate holdout.

No aid has reached Fallujah since September last year and residents have been living on dates, dirty water from the Euphrates and animal feed.

The Norwegian Refugee Council said another 300 families managed to flee areas around Fallujah in the past 24 hours, bringing to about 5,000 the number of people who escaped since the start of the operation.