Anbar to be freed of Islamic State, says Iraq PM

"Our next... battle will be here in the land of Anbar to completely liberate it," his office quoted him as saying.

Military sources say Iraqi troops are fighting IS east of the regional capital Ramadi.

Government forces recaptured Tikrit from IS last week after it fell to the jihadist militants in June.

'Will prevail'

Mr Abadi said in a post on his official Facebook page (in Arabic): "We will prevail in Anbar as we prevailed in Tikrit."

Army officers said IS militants had been driven back in the Sijariya area east of Ramadi.

Anbar, a heavily-Sunni area stretching west from the capital Baghdad to the Syrian border, is the country's biggest province. Most of its towns and cities are held by IS or other Sunni insurgents.

Falluja, a key city in the region overrun by IS, is said to be blockaded on three sides amidst a build-up for an assault.

In addition to Iraqi army units, Shia militia forces are also reported to be moving in to the province from areas to the south of Baghdad.

The use of Shia irregulars in heavily-Sunni heartlands is controversial although PM Abadi is organising the mobilisation and arming of local Sunni tribes, reports the BBC's Middle East correspondent Jim Muir.

Efforts to dislodge Sunni militants from cities like Falluja have failed in the past, so recapturing the whole of the huge Anbar province is clearly a major undertaking, our correspondent notes.

But the government is evidently hoping to keep up the momentum of the defeat inflicted on the militants at Tikrit, he adds.

Iraqi officials have argued for some time that to isolate IS in its bastions along the Syrian border, Anbar should be the next major target either on its own or in a parallel attack on the northern province of Nineveh.

US troops occupied Anbar for eight years, suffering heavy losses in the process to Sunni insurgents.